ID##Title##Published##Solved By
1##Multiples of 3 or 5##2001-10-05 17:00:00##849634
2##Even Fibonacci Numbers##2001-10-19 17:00:00##679676
3##Largest Prime Factor##2001-11-02 18:00:00##512772
4##Largest Palindrome Product##2001-11-16 18:00:00##453398
5##Smallest Multiple##2001-11-30 18:00:00##439880
6##Sum Square Difference##2001-12-14 18:00:00##444926
7##10 001st Prime##2001-12-28 18:00:00##387743
8##Largest Product in a Series##2002-01-11 18:00:00##330563
9##Special Pythagorean Triplet##2002-01-25 18:00:00##335998
10##Summation of Primes##2002-02-08 18:00:00##315470
11##Largest Product in a Grid##2002-02-22 18:00:00##236671
12##Highly Divisible Triangular Number##2002-03-08 18:00:00##232992
13##Large Sum##2002-03-22 18:00:00##233766
14##Longest Collatz Sequence##2002-04-05 17:00:00##238161
15##Lattice Paths##2002-04-19 17:00:00##202180
16##Power Digit Sum##2002-05-03 17:00:00##236489
17##Number Letter Counts##2002-05-17 17:00:00##169702
18##Maximum Path Sum I##2002-05-31 17:00:00##164108
19##Counting Sundays##2002-06-14 17:00:00##153887
20##Factorial Digit Sum##2002-06-21 17:00:00##207025
21##Amicable Numbers##2002-07-05 17:00:00##169206
22##Names Scores##2002-07-19 17:00:00##155896
23##Non-Abundant Sums##2002-08-02 17:00:00##128739
24##Lexicographic Permutations##2002-08-16 17:00:00##137837
25##$1000$-digit Fibonacci Number##2002-08-30 17:00:00##175369
26##Reciprocal Cycles##2002-09-13 17:00:00##104850
27##Quadratic Primes##2002-09-27 17:00:00##108348
28##Number Spiral Diagonals##2002-10-11 17:00:00##127074
29##Distinct Powers##2002-10-25 17:00:00##128011
30##Digit Fifth Powers##2002-11-08 18:00:00##132862
31##Coin Sums##2002-11-22 18:00:00##104589
32##Pandigital Products##2002-12-06 18:00:00##89185
33##Digit Cancelling Fractions##2002-12-20 18:00:00##89068
34##Digit Factorials##2003-01-03 18:00:00##115220
35##Circular Primes##2003-01-17 18:00:00##103197
36##Double-base Palindromes##2003-01-31 18:00:00##107805
37##Truncatable Primes##2003-02-14 18:00:00##91162
38##Pandigital Multiples##2003-02-28 18:00:00##78332
39##Integer Right Triangles##2003-03-14 18:00:00##90116
40##Champernowne's Constant##2003-03-28 18:00:00##97121
41##Pandigital Prime##2003-04-11 17:00:00##84456
42##Coded Triangle Numbers##2003-04-25 17:00:00##90141
43##Sub-string Divisibility##2003-05-09 17:00:00##74480
44##Pentagon Numbers##2003-05-23 17:00:00##73018
45##Triangular, Pentagonal, and Hexagonal##2003-06-06 17:00:00##86539
46##Goldbach's Other Conjecture##2003-06-20 17:00:00##76580
47##Distinct Primes Factors##2003-07-04 17:00:00##72037
48##Self Powers##2003-07-18 17:00:00##123163
49##Prime Permutations##2003-08-01 17:00:00##71631
50##Consecutive Prime Sum##2003-08-15 17:00:00##76769
51##Prime Digit Replacements##2003-08-29 17:00:00##44015
52##Permuted Multiples##2003-09-12 17:00:00##79036
53##Combinatoric Selections##2003-09-26 17:00:00##71606
54##Poker Hands##2003-10-10 17:00:00##44750
55##Lychrel Numbers##2003-10-24 17:00:00##65446
56##Powerful Digit Sum##2003-11-07 18:00:00##70769
57##Square Root Convergents##2003-11-21 18:00:00##51874
58##Spiral Primes##2003-12-05 18:00:00##49819
59##XOR Decryption##2003-12-19 18:00:00##49655
60##Prime Pair Sets##2004-01-02 18:00:00##34851
61##Cyclical Figurate Numbers##2004-01-16 18:00:00##32487
62##Cubic Permutations##2004-01-30 18:00:00##40062
63##Powerful Digit Counts##2004-02-13 18:00:00##52813
64##Odd Period Square Roots##2004-02-27 18:00:00##28164
65##Convergents of $e$##2004-03-12 18:00:00##37196
66##Diophantine Equation##2004-03-26 18:00:00##25388
67##Maximum Path Sum II##2004-04-09 17:00:00##106871
68##Magic 5-gon Ring##2004-04-23 17:00:00##26237
69##Totient Maximum##2004-05-07 17:00:00##43659
70##Totient Permutation##2004-05-21 17:00:00##28328
71##Ordered Fractions##2004-06-04 17:00:00##36331
72##Counting Fractions##2004-06-18 17:00:00##28292
73##Counting Fractions in a Range##2004-07-02 17:00:00##31161
74##Digit Factorial Chains##2004-07-16 17:00:00##33522
75##Singular Integer Right Triangles##2004-07-30 17:00:00##23152
76##Counting Summations##2004-08-13 17:00:00##35176
77##Prime Summations##2004-08-27 17:00:00##24589
78##Coin Partitions##2004-09-10 17:00:00##22027
79##Passcode Derivation##2004-09-17 17:00:00##46452
80##Square Root Digital Expansion##2004-10-08 17:00:00##24959
81##Path Sum: Two Ways##2004-10-22 17:00:00##41402
82##Path Sum: Three Ways##2004-11-05 18:00:00##26150
83##Path Sum: Four Ways##2004-11-19 18:00:00##22842
84##Monopoly Odds##2004-12-03 18:00:00##16283
85##Counting Rectangles##2004-12-17 18:00:00##30566
86##Cuboid Route##2005-01-07 18:00:00##16448
87##Prime Power Triples##2005-01-21 18:00:00##26212
88##Product-sum Numbers##2005-02-04 18:00:00##13511
89##Roman Numerals##2005-02-18 18:00:00##25729
90##Cube Digit Pairs##2005-03-04 18:00:00##14819
91##Right Triangles with Integer Coordinates##2005-03-18 18:00:00##19783
92##Square Digit Chains##2005-04-01 17:00:00##49545
93##Arithmetic Expressions##2005-04-15 17:00:00##15367
94##Almost Equilateral Triangles##2005-04-29 17:00:00##16356
95##Amicable Chains##2005-05-13 17:00:00##18618
96##Su Doku##2005-05-27 17:00:00##21261
97##Large Non-Mersenne Prime##2005-06-10 17:00:00##50263
98##Anagramic Squares##2005-06-17 17:00:00##14798
99##Largest Exponential##2005-07-01 17:00:00##37395
100##Arranged Probability##2005-07-15 17:00:00##21034
101##Optimum Polynomial##2005-07-29 17:00:00##15192
102##Triangle Containment##2005-08-12 17:00:00##26815
103##Special Subset Sums: Optimum##2005-08-26 17:00:00##10625
104##Pandigital Fibonacci Ends##2005-09-09 17:00:00##20048
105##Special Subset Sums: Testing##2005-09-23 17:00:00##10523
106##Special Subset Sums: Meta-testing##2005-10-07 17:00:00##8477
107##Minimal Network##2005-10-21 17:00:00##13642
108##Diophantine Reciprocals I##2005-11-04 18:00:00##15813
109##Darts##2005-11-18 18:00:00##10548
110##Diophantine Reciprocals II##2005-12-02 18:00:00##10520
111##Primes with Runs##2005-12-16 18:00:00##9499
112##Bouncy Numbers##2005-12-30 18:00:00##30146
113##Non-bouncy Numbers##2006-02-10 18:00:00##13783
114##Counting Block Combinations I##2006-02-17 18:00:00##13707
115##Counting Block Combinations II##2006-02-24 18:00:00##12550
116##Red, Green or Blue Tiles##2006-03-03 18:00:00##15132
117##Red, Green, and Blue Tiles##2006-03-10 18:00:00##14051
118##Pandigital Prime Sets##2006-03-24 18:00:00##9136
119##Digit Power Sum##2006-04-07 17:00:00##15386
120##Square Remainders##2006-04-21 17:00:00##17058
121##Disc Game Prize Fund##2006-05-19 17:00:00##12212
122##Efficient Exponentiation##2006-06-02 17:00:00##9979
123##Prime Square Remainders##2006-06-16 17:00:00##14279
124##Ordered Radicals##2006-07-14 17:00:00##16825
125##Palindromic Sums##2006-08-04 17:00:00##16701
126##Cuboid Layers##2006-08-18 17:00:00##6315
127##abc-hits##2006-09-01 17:00:00##8176
128##Hexagonal Tile Differences##2006-09-29 17:00:00##6588
129##Repunit Divisibility##2006-10-27 17:00:00##8112
130##Composites with Prime Repunit Property##2006-10-27 17:00:00##7635
131##Prime Cube Partnership##2006-11-10 18:00:00##9442
132##Large Repunit Factors##2006-12-01 18:00:00##8185
133##Repunit Nonfactors##2006-12-01 18:00:00##7232
134##Prime Pair Connection##2006-12-15 18:00:00##9084
135##Same Differences##2006-12-29 18:00:00##8299
136##Singleton Difference##2006-12-29 18:00:00##7402
137##Fibonacci Golden Nuggets##2007-01-12 18:00:00##7365
138##Special Isosceles Triangles##2007-01-20 11:00:00##7524
139##Pythagorean Tiles##2007-01-27 09:00:00##7358
140##Modified Fibonacci Golden Nuggets##2007-02-03 07:00:00##5804
141##Square Progressive Numbers##2007-02-17 05:00:00##5356
142##Perfect Square Collection##2007-02-24 01:00:00##7399
143##Torricelli Triangles##2007-03-02 21:00:00##3824
144##Laser Beam Reflections ##2007-03-09 17:00:00##7988
145##Reversible Numbers##2007-03-16 13:00:00##20066
146##Investigating a Prime Pattern ##2007-03-24 09:00:00##6702
147##Rectangles in Cross-hatched Grids##2007-03-31 05:00:00##4104
148##Exploring Pascal's Triangle##2007-04-07 01:00:00##6590
149##Maximum-sum Subsequence##2007-04-13 21:00:00##6235
150##Sub-triangle Sums##2007-04-13 21:00:00##5163
151##A Preference for A5##2007-04-20 17:00:00##7107
152##Sums of Square Reciprocals##2007-04-27 13:00:00##3708
153##Investigating Gaussian Integers##2007-05-05 09:00:00##3611
154##Exploring Pascal's Pyramid##2007-05-12 05:00:00##3585
155##Counting Capacitor Circuits##2007-05-19 01:00:00##4771
156##Counting Digits##2007-05-25 21:00:00##3401
157##Base-10 Diophantine Reciprocal##2007-06-01 17:00:00##3682
158##Lexicographical Neighbours##2007-06-15 13:00:00##4774
159##Digital Root Sums of Factorisations##2007-06-30 13:00:00##4367
160##Factorial Trailing Digits##2007-09-07 13:00:00##4669
161##Triominoes##2007-09-21 17:00:00##2997
162##Hexadecimal Numbers##2007-10-05 21:00:00##6694
163##Cross-hatched Triangles##2007-10-13 01:00:00##2586
164##Three Consecutive Digital Sum Limit##2007-10-20 05:00:00##7400
165##Intersections##2007-10-27 09:00:00##3559
166##Criss Cross##2007-11-03 13:00:00##5340
167##Investigating Ulam Sequences##2007-11-09 13:00:00##2424
168##Number Rotations##2007-11-16 17:00:00##3558
169##Sums of Powers of Two##2007-11-23 21:00:00##6554
170##Pandigital Concatenating Products##2007-12-01 01:00:00##2761
171##Square Sum of the Digital Squares##2007-12-08 05:00:00##3776
172##Few Repeated Digits##2007-12-15 09:00:00##4985
173##Hollow Square Laminae I##2007-12-22 13:00:00##11178
174##Hollow Square Laminae II##2007-12-22 13:00:00##7478
175##Fractions and Sum of Powers of Two##2007-12-28 13:00:00##2541
176##Common Cathetus Right-angled Triangles##2008-01-04 17:00:00##2642
177##Integer Angled Quadrilaterals##2008-01-11 21:00:00##1922
178##Step Numbers##2008-01-19 01:00:00##4472
179##Consecutive Positive Divisors##2008-01-26 05:00:00##13692
180##Golden Triplets##2008-02-02 09:00:00##2270
181##Grouping Two Different Coloured Objects##2008-02-09 13:00:00##2796
182##RSA Encryption##2008-02-15 13:00:00##3542
183##Maximum Product of Parts##2008-02-22 17:00:00##5899
184##Triangles Containing the Origin##2008-02-29 21:00:00##2330
185##Number Mind##2008-03-08 01:00:00##4081
186##Connectedness of a Network##2008-03-15 05:00:00##3857
187##Semiprimes##2008-03-22 09:00:00##13528
188##Hyperexponentiation##2008-04-04 13:00:00##7944
189##Tri-colouring a Triangular Grid##2008-04-11 16:00:00##2840
190##Maximising a Weighted Product##2008-04-18 21:00:00##5314
191##Prize Strings##2008-04-26 00:00:00##8767
192##Best Approximations##2008-05-03 04:00:00##2352
193##Squarefree Numbers##2008-05-10 12:00:00##4539
194##Coloured Configurations##2008-05-17 09:00:00##2041
195##$60$-degree Triangle Inscribed Circles##2008-05-23 13:00:00##2077
196##Prime Triplets##2008-05-30 17:00:00##3490
197##A Recursively Defined Sequence##2008-06-06 21:00:00##6102
198##Ambiguous Numbers##2008-06-14 01:00:00##1721
199##Iterative Circle Packing##2008-06-21 05:00:00##2677
200##Prime-proof Squbes##2008-06-28 09:00:00##3262
201##Subsets with a Unique Sum##2008-07-05 13:00:00##3212
202##Laserbeam##2008-07-05 13:00:00##3355
203##Squarefree Binomial Coefficients##2008-09-06 13:00:00##10990
204##Generalised Hamming Numbers##2008-09-06 13:00:00##8945
205##Dice Game##2008-09-06 13:00:00##17708
206##Concealed Square##2008-09-06 13:00:00##28621
207##Integer Partition Equations##2008-09-06 13:00:00##5802
208##Robot Walks##2008-09-12 13:00:00##2420
209##Circular Logic##2008-09-19 17:00:00##3285
210##Obtuse Angled Triangles##2008-09-26 21:00:00##2317
211##Divisor Square Sum##2008-10-04 01:00:00##5368
212##Combined Volume of Cuboids##2008-10-11 05:00:00##1934
213##Flea Circus##2008-10-18 09:00:00##3117
214##Totient Chains##2008-10-25 13:00:00##6509
215##Crack-free Walls##2008-10-31 13:00:00##4583
216##The Primality of $2n^2 - 1$##2008-11-07 17:00:00##5296
217##Balanced Numbers##2008-11-14 21:00:00##2127
218##Perfect Right-angled Triangles##2008-11-22 01:00:00##3790
219##Skew-cost Coding##2008-11-29 05:00:00##2027
220##Heighway Dragon##2008-12-06 09:00:00##2752
221##Alexandrian Integers##2008-12-13 13:00:00##2829
222##Sphere Packing##2008-12-19 13:00:00##2733
223##Almost Right-angled Triangles I##2008-12-26 17:00:00##2142
224##Almost Right-angled Triangles II##2008-12-26 17:00:00##1779
225##Tribonacci Non-divisors##2008-12-26 17:00:00##5532
226##A Scoop of Blancmange##2009-01-02 21:00:00##2344
227##The Chase##2009-01-10 01:00:00##2818
228##Minkowski Sums##2009-01-17 05:00:00##1875
229##Four Representations Using Squares##2009-01-24 09:00:00##1991
230##Fibonacci Words##2009-01-31 13:00:00##3577
231##Prime Factorisation of Binomial Coefficients##2009-02-06 13:00:00##6818
232##The Race##2009-02-13 17:00:00##2404
233##Lattice Points on a Circle##2009-02-20 21:00:00##3027
234##Semidivisible Numbers##2009-02-28 01:00:00##4028
235##An Arithmetic Geometric Sequence##2009-03-07 05:00:00##5988
236##Luxury Hampers##2009-03-14 09:00:00##1388
237##Tours on a $4 \times N$ Playing Board##2009-03-21 13:00:00##2179
238##Infinite String Tour##2009-03-29 14:00:00##1400
239##Twenty-two Foolish Primes##2009-04-03 16:00:00##2414
240##Top Dice##2009-04-10 21:00:00##2832
241##Perfection Quotients##2009-04-18 01:00:00##1403
242##Odd Triplets##2009-04-25 05:00:00##1517
243##Resilience##2009-05-02 09:00:00##11224
244##Sliders##2009-05-09 13:00:00##1814
245##Coresilience##2009-05-15 13:00:00##1282
246##Tangents to an Ellipse##2009-05-22 16:00:00##1270
247##Squares Under a Hyperbola##2009-05-29 20:00:00##2035
248##Euler's Totient Function Equals 13!##2009-06-06 00:00:00##1819
249##Prime Subset Sums##2009-06-13 04:00:00##3310
250##$250250$##2009-06-13 04:00:00##3946
251##Cardano Triplets##2009-06-20 08:00:00##1939
252##Convex Holes##2009-06-27 12:00:00##1258
253##Tidying Up A##2009-08-28 12:00:00##1488
254##Sums of Digit Factorials##2009-09-04 16:00:00##1399
255##Rounded Square Roots##2009-09-11 20:00:00##1277
256##Tatami-Free Rooms##2009-09-19 00:00:00##1134
257##Angular Bisectors##2009-09-26 04:00:00##1080
258##A Lagged Fibonacci Sequence##2009-10-03 08:00:00##2191
259##Reachable Numbers##2009-10-10 12:00:00##2050
260##Stone Game##2009-10-16 12:00:00##1797
261##Pivotal Square Sums##2009-10-23 16:00:00##1088
262##Mountain Range##2009-10-30 21:00:00##1095
263##An Engineers' Dream Come True##2009-11-07 01:00:00##1488
264##Triangle Centres##2009-11-14 05:00:00##929
265##Binary Circles##2009-11-21 09:00:00##5220
266##Pseudo Square Root##2009-11-28 13:00:00##2300
267##Billionaire##2009-12-04 13:00:00##4267
268##At Least Four Distinct Prime Factors Less Than 100##2009-12-11 17:00:00##2009
269##Polynomials with at Least One Integer Root##2009-12-19 09:00:00##1184
270##Cutting Squares##2009-12-26 01:00:00##984
271##Modular Cubes, Part 1##2010-01-02 05:00:00##3186
272##Modular Cubes, Part 2##2010-01-02 05:00:00##1450
273##Sum of Squares##2010-01-09 13:00:00##1901
274##Divisibility Multipliers##2010-01-15 13:00:00##2127
275##Balanced Sculptures##2010-01-22 17:00:00##949
276##Primitive Triangles##2010-01-29 21:00:00##1528
277##A Modified Collatz Sequence##2010-02-06 01:00:00##4089
278##Linear Combinations of Semiprimes##2010-02-13 05:00:00##1516
279##Triangles with Integral Sides and an Integral Angle ##2010-02-20 09:00:00##1118
280##Ant and Seeds##2010-02-27 13:00:00##1502
281##Pizza Toppings##2010-03-05 13:00:00##1442
282##The Ackermann Function##2010-03-12 17:00:00##1496
283##Integer Sided Triangles with Integral Area/perimeter Ratio##2010-03-19 21:00:00##970
284##Steady Squares##2010-03-27 01:00:00##1722
285##Pythagorean Odds##2010-04-03 04:00:00##1687
286##Scoring Probabilities##2010-04-03 04:00:00##2842
287##Quadtree Encoding (a Simple Compression Algorithm)##2010-04-10 08:00:00##1960
288##An Enormous Factorial##2010-04-17 12:00:00##2301
289##Eulerian Cycles##2010-04-23 12:00:00##846
290##Digital Signature##2010-04-30 16:00:00##1426
291##Panaitopol Primes##2010-05-07 20:00:00##2026
292##Pythagorean Polygons##2010-05-15 00:00:00##897
293##Pseudo-Fortunate Numbers##2010-05-22 04:00:00##3866
294##Sum of Digits - Experience #23##2010-05-29 08:00:00##1341
295##Lenticular Holes##2010-06-05 12:00:00##754
296##Angular Bisector and Tangent##2010-06-11 12:00:00##1007
297##Zeckendorf Representation##2010-06-18 16:00:00##3640
298##Selective Amnesia##2010-06-25 20:00:00##1009
299##Three Similar Triangles##2010-07-03 00:00:00##943
300##Protein Folding##2010-09-04 12:00:00##1523
301##Nim##2010-09-11 15:00:00##8149
302##Strong Achilles Numbers##2010-09-18 18:00:00##1141
303##Multiples with Small Digits##2010-09-25 21:00:00##4599
304##Primonacci##2010-10-03 00:00:00##2936
305##Reflexive Position##2010-10-10 03:00:00##929
306##Paper-strip Game##2010-10-17 06:00:00##1756
307##Chip Defects##2010-10-24 09:00:00##2226
308##An Amazing Prime-generating Automaton##2010-10-30 12:00:00##1125
309##Integer Ladders##2010-11-06 16:00:00##1224
310##Nim Square##2010-11-13 19:00:00##1675
311##Biclinic Integral Quadrilaterals##2010-11-20 22:00:00##710
312##Cyclic Paths on Sierpiński Graphs##2010-11-28 01:00:00##1235
313##Sliding Game##2010-12-05 04:00:00##2283
314##The Mouse on the Moon##2010-12-12 07:00:00##812
315##Digital Root Clocks##2010-12-19 10:00:00##4252
316##Numbers in Decimal Expansions##2010-12-25 13:00:00##994
317##Firecracker##2011-01-01 16:00:00##3436
318##2011 Nines##2011-01-01 16:00:00##1353
319##Bounded Sequences##2011-01-08 19:00:00##700
320##Factorials Divisible by a Huge Integer##2011-01-15 22:00:00##1296
321##Swapping Counters##2011-01-23 01:00:00##2278
322##Binomial Coefficients Divisible by 10##2011-01-30 04:00:00##747
323##Bitwise-OR Operations on Random Integers##2011-02-06 07:00:00##4909
324##Building a Tower##2011-02-13 10:00:00##1061
325##Stone Game II##2011-02-19 13:00:00##957
326##Modulo Summations##2011-02-26 16:00:00##834
327##Rooms of Doom##2011-03-05 19:00:00##1543
328##Lowest-cost Search##2011-03-12 22:00:00##753
329##Prime Frog##2011-03-20 01:00:00##3253
330##Euler's Number##2011-03-27 04:00:00##823
331##Cross Flips##2011-04-03 07:00:00##755
332##Spherical Triangles##2011-04-10 09:00:00##920
333##Special Partitions##2011-04-16 12:00:00##1721
334##Spilling the Beans##2011-04-23 15:00:00##759
335##Gathering the Beans##2011-04-23 15:00:00##816
336##Maximix Arrangements##2011-04-30 18:00:00##2731
337##Totient Stairstep Sequences##2011-05-07 21:00:00##832
338##Cutting Rectangular Grid Paper##2011-05-15 00:00:00##617
339##Peredur Fab Efrawg##2011-05-22 03:00:00##839
340##Crazy Function##2011-05-29 06:00:00##1594
341##Golomb's Self-describing Sequence##2011-06-05 09:00:00##1303
342##The Totient of a Square Is a Cube##2011-06-11 12:00:00##1151
343##Fractional Sequences##2011-06-18 15:00:00##1841
344##Silver Dollar Game##2011-06-25 18:00:00##628
345##Matrix Sum##2011-09-03 15:00:00##7182
346##Strong Repunits##2011-09-03 15:00:00##5661
347##Largest Integer Divisible by Two Primes##2011-09-03 15:00:00##5784
348##Sum of a Square and a Cube##2011-09-03 15:00:00##4034
349##Langton's Ant##2011-09-03 15:00:00##2552
350##Constraining the Least Greatest and the Greatest Least##2011-09-10 18:00:00##769
351##Hexagonal Orchards##2011-09-17 21:00:00##3378
352##Blood Tests##2011-10-02 00:00:00##907
353##Risky Moon##2011-10-09 03:00:00##784
354##Distances in a Bee's Honeycomb ##2011-10-16 06:00:00##712
355##Maximal Coprime Subset##2011-10-23 09:00:00##839
356##Largest Roots of Cubic Polynomials##2011-10-29 12:00:00##918
357##Prime Generating Integers##2011-11-05 16:00:00##9959
358##Cyclic Numbers##2011-11-12 19:00:00##2104
359##Hilbert's New Hotel##2011-11-19 22:00:00##2010
360##Scary Sphere##2011-11-27 01:00:00##842
361##Subsequence of Thue-Morse Sequence##2011-12-04 04:00:00##581
362##Squarefree Factors##2011-12-11 07:00:00##738
363##Bézier Curves##2011-12-18 10:00:00##1583
364##Comfortable Distance##2011-12-24 13:00:00##1001
365##A Huge Binomial Coefficient##2011-12-31 16:00:00##1747
366##Stone Game III##2012-01-07 19:00:00##980
367##Bozo Sort##2012-01-14 22:00:00##795
368##A Kempner-like Series##2012-01-22 01:00:00##807
369##Badugi##2012-01-29 04:00:00##731
370##Geometric Triangles##2012-02-05 07:00:00##806
371##Licence Plates##2012-02-12 10:00:00##2175
372##Pencils of Rays##2012-02-18 13:00:00##628
373##Circumscribed Circles##2012-02-25 16:00:00##583
374##Maximum Integer Partition Product##2012-03-03 19:00:00##987
375##Minimum of Subsequences##2012-03-10 22:00:00##1239
376##Nontransitive Sets of Dice##2012-03-18 01:00:00##496
377##Sum of Digits - Experience #13##2012-03-25 04:00:00##1123
378##Triangle Triples##2012-04-01 06:00:00##1247
379##Least Common Multiple Count##2012-04-08 10:00:00##802
380##Amazing Mazes!##2012-04-14 13:00:00##776
381##$(\text{prime}-k)$ Factorial##2012-04-21 16:00:00##5642
382##Generating Polygons##2012-04-28 19:00:00##568
383##Divisibility Comparison Between Factorials##2012-05-05 22:00:00##741
384##Rudin-Shapiro Sequence##2012-05-13 01:00:00##531
385##Ellipses Inside Triangles##2012-05-20 04:00:00##506
386##Maximum Length of an Antichain##2012-05-27 07:00:00##1063
387##Harshad Numbers##2012-06-03 10:00:00##5827
388##Distinct Lines##2012-06-09 13:00:00##872
389##Platonic Dice##2012-06-16 16:00:00##2006
390##Triangles with Non Rational Sides and Integral Area##2012-06-23 19:00:00##812
391##Hopping Game##2012-06-30 22:00:00##483
392##Enmeshed Unit Circle##2012-09-01 13:00:00##1085
393##Migrating Ants##2012-09-08 16:00:00##1098
394##Eating Pie##2012-09-15 19:00:00##816
395##Pythagorean Tree##2012-09-22 22:00:00##989
396##Weak Goodstein Sequence##2012-09-30 01:00:00##930
397##Triangle on Parabola##2012-10-07 04:00:00##475
398##Cutting Rope##2012-10-14 07:00:00##622
399##Squarefree Fibonacci Numbers##2012-10-21 10:00:00##875
400##Fibonacci Tree Game##2012-10-27 13:00:00##726
401##Sum of Squares of Divisors##2012-11-10 16:00:00##3483
402##Integer-valued Polynomials##2012-11-17 19:00:00##666
403##Lattice Points Enclosed by Parabola and Line##2012-11-24 22:00:00##580
404##Crisscross Ellipses##2012-12-02 01:00:00##542
405##A Rectangular Tiling##2012-12-09 04:00:00##920
406##Guessing Game##2012-12-16 07:00:00##627
407##Idempotents##2012-12-23 10:00:00##3232
408##Admissible Paths Through a Grid##2012-12-29 13:00:00##858
409##Nim Extreme##2013-01-05 16:00:00##687
410##Circle and Tangent Line##2013-01-12 19:00:00##484
411##Uphill Paths##2013-01-19 22:00:00##983
412##Gnomon Numbering##2013-01-27 01:00:00##773
413##One-child Numbers##2013-02-03 04:00:00##643
414##Kaprekar Constant##2013-02-10 07:00:00##480
415##Titanic Sets##2013-02-17 10:00:00##637
416##A Frog's Trip##2013-02-23 13:00:00##514
417##Reciprocal Cycles II##2013-03-02 16:00:00##1360
418##Factorisation Triples##2013-03-09 19:00:00##973
419##Look and Say Sequence##2013-03-16 22:00:00##715
420##$2 \times 2$ Positive Integer Matrix##2013-03-24 01:00:00##695
421##Prime Factors of $n^{15}+1$##2013-03-31 03:00:00##971
422##Sequence of Points on a Hyperbola##2013-04-07 06:00:00##489
423##Consecutive Die Throws##2013-04-14 09:00:00##777
424##Kakuro##2013-04-20 12:00:00##626
425##Prime Connection##2013-04-27 15:00:00##1995
426##Box-Ball System##2013-05-04 18:00:00##438
427##$n$-sequences##2013-05-11 21:00:00##588
428##Necklace of Circles##2013-05-19 00:00:00##458
429##Sum of Squares of Unitary Divisors##2013-05-26 03:00:00##3337
430##Range Flips##2013-06-02 06:00:00##1144
431##Square Space Silo##2013-06-09 09:00:00##935
432##Totient Sum##2013-06-15 12:00:00##780
433##Steps in Euclid's Algorithm##2013-06-22 15:00:00##717
434##Rigid Graphs##2013-06-29 18:00:00##546
435##Polynomials of Fibonacci Numbers##2013-09-07 15:00:00##1574
436##Unfair Wager##2013-09-14 18:00:00##685
437##Fibonacci Primitive Roots##2013-09-21 21:00:00##1240
438##Integer Part of Polynomial Equation's Solutions##2013-09-29 00:00:00##476
439##Sum of Sum of Divisors##2013-10-06 03:00:00##698
440##GCD and Tiling##2013-10-13 06:00:00##616
441##The Inverse Summation of Coprime Couples##2013-10-20 09:00:00##589
442##Eleven-free Integers##2013-10-26 12:00:00##637
443##GCD Sequence##2013-11-02 16:00:00##1658
444##The Roundtable Lottery##2013-11-09 19:00:00##513
445##Retractions A##2013-11-16 22:00:00##636
446##Retractions B##2013-11-16 22:00:00##604
447##Retractions C##2013-11-16 22:00:00##578
448##Average Least Common Multiple##2013-11-24 01:00:00##577
449##Chocolate Covered Candy##2013-12-08 04:00:00##1260
450##Hypocycloid and Lattice Points##2013-12-15 07:00:00##401
451##Modular Inverses##2013-12-22 10:00:00##1996
452##Long Products##2013-12-28 13:00:00##882
453##Lattice Quadrilaterals##2014-01-04 16:00:00##446
454##Diophantine Reciprocals III##2014-01-11 19:00:00##735
455##Powers with Trailing Digits##2014-01-18 22:00:00##1062
456##Triangles Containing the Origin II##2014-01-26 01:00:00##622
457##A Polynomial Modulo the Square of a Prime##2014-02-02 04:00:00##1167
458##Permutations of Project##2014-02-09 07:00:00##1305
459##Flipping Game##2014-02-16 10:00:00##458
460##An Ant on the Move##2014-02-22 13:00:00##515
461##Almost Pi##2014-03-01 16:00:00##1647
462##Permutation of 3-smooth Numbers##2014-03-08 19:00:00##543
463##A Weird Recurrence Relation##2014-03-15 22:00:00##1537
464##Möbius Function and Intervals##2014-03-23 01:00:00##523
465##Polar Polygons##2014-03-30 04:00:00##424
466##Distinct Terms in a Multiplication Table##2014-04-06 06:00:00##527
467##Superinteger##2014-04-13 09:00:00##684
468##Smooth Divisors of Binomial Coefficients##2014-04-19 12:00:00##469
469##Empty Chairs##2014-04-26 15:00:00##1053
470##Super Ramvok##2014-05-03 18:00:00##405
471##Triangle Inscribed in Ellipse##2014-05-10 21:00:00##409
472##Comfortable Distance II##2014-05-18 00:00:00##412
473##Phigital Number Base##2014-05-25 03:00:00##1034
474##Last Digits of Divisors##2014-06-01 06:00:00##641
475##Music Festival##2014-06-08 09:00:00##706
476##Circle Packing II##2014-06-14 12:00:00##592
477##Number Sequence Game##2014-08-23 15:00:00##413
478##Mixtures##2014-08-30 18:00:00##445
479##Roots on the Rise##2014-09-06 21:00:00##1779
480##The Last Question##2014-09-14 00:00:00##856
481##Chef Showdown##2014-09-21 03:00:00##426
482##The Incenter of a Triangle##2014-09-28 06:00:00##379
483##Repeated Permutation##2014-10-05 09:00:00##496
484##Arithmetic Derivative##2014-10-11 12:00:00##688
485##Maximum Number of Divisors##2014-10-18 15:00:00##1617
486##Palindrome-containing Strings##2014-10-25 18:00:00##436
487##Sums of Power Sums##2014-11-01 22:00:00##960
488##Unbalanced Nim##2014-11-09 01:00:00##379
489##Common Factors Between Two Sequences##2014-11-16 04:00:00##442
490##Jumping Frog##2014-11-23 07:00:00##510
491##Double Pandigital Number Divisible by $11$##2014-11-30 10:00:00##2760
492##Exploding Sequence##2014-12-06 13:00:00##541
493##Under the Rainbow##2014-12-13 16:00:00##6711
494##Collatz Prefix Families##2014-12-20 19:00:00##425
495##Writing $n$ as the Product of $k$ Distinct Positive Integers##2014-12-27 22:00:00##598
496##Incenter and Circumcenter of Triangle##2015-01-04 01:00:00##517
497##Drunken Tower of Hanoi##2015-01-11 04:00:00##831
498##Remainder of Polynomial Division##2015-01-18 07:00:00##761
499##St. Petersburg Lottery##2015-01-25 10:00:00##621
500##Problem 500!!!##2015-01-31 13:00:00##5190
501##Eight Divisors##2015-01-31 13:00:00##1831
502##Counting Castles##2015-02-07 16:00:00##523
503##Compromise or Persist##2015-02-14 19:00:00##504
504##Square on the Inside##2015-02-21 22:00:00##3960
505##Bidirectional Recurrence##2015-03-01 01:00:00##356
506##Clock Sequence##2015-03-08 04:00:00##1264
507##Shortest Lattice Vector##2015-03-15 07:00:00##356
508##Integers in Base $i-1$##2015-03-22 10:00:00##386
509##Divisor Nim##2015-03-28 13:00:00##878
510##Tangent Circles##2015-04-04 15:00:00##1425
511##Sequences with Nice Divisibility Properties##2015-04-11 18:00:00##633
512##Sums of Totients of Powers##2015-04-18 21:00:00##2019
513##Integral Median##2015-04-26 00:00:00##466
514##Geoboard Shapes##2015-05-03 03:00:00##377
515##Dissonant Numbers##2015-05-10 06:00:00##682
516##$5$-smooth Totients##2015-05-17 09:00:00##2051
517##A Real Recursion##2015-05-23 12:00:00##671
518##Prime Triples and Geometric Sequences##2015-05-30 15:00:00##2170
519##Tricoloured Coin Fountains##2015-06-06 18:00:00##530
520##Simbers##2015-06-13 21:00:00##661
521##Smallest Prime Factor##2015-06-21 00:00:00##1072
522##Hilbert's Blackout##2015-06-28 03:00:00##424
523##First Sort I##2015-09-06 06:00:00##1424
524##First Sort II##2015-09-06 06:00:00##352
525##Rolling Ellipse##2015-09-13 09:00:00##738
526##Largest Prime Factors of Consecutive Numbers##2015-09-19 12:00:00##484
527##Randomized Binary Search##2015-09-26 15:00:00##1053
528##Constrained Sums##2015-10-03 18:00:00##478
529##$10$-substrings##2015-10-10 21:00:00##439
530##GCD of Divisors##2015-10-18 00:00:00##669
531##Chinese Leftovers##2015-10-25 04:00:00##1614
532##Nanobots on Geodesics##2015-11-01 07:00:00##457
533##Minimum Values of the Carmichael Function##2015-11-08 10:00:00##495
534##Weak Queens##2015-11-14 13:00:00##482
535##Fractal Sequence##2015-11-21 16:00:00##427
536##Modulo Power Identity ##2015-11-28 19:00:00##442
537##Counting Tuples##2015-12-05 22:00:00##954
538##Maximum Quadrilaterals##2015-12-13 01:00:00##483
539##Odd Elimination##2015-12-20 04:00:00##1154
540##Counting Primitive Pythagorean Triples##2015-12-27 07:00:00##949
541##Divisibility of Harmonic Number Denominators##2016-01-03 10:00:00##378
542##Geometric Progression with Maximum Sum##2016-01-09 13:00:00##361
543##Prime-Sum Numbers##2016-01-16 16:00:00##1051
544##Chromatic Conundrum##2016-01-23 19:00:00##417
545##Faulhaber's Formulas##2016-01-30 22:00:00##792
546##The Floor's Revenge##2016-02-07 01:00:00##389
547##Distance of Random Points Within Hollow Square Laminae##2016-02-14 04:00:00##360
548##Gozinta Chains##2016-02-21 07:00:00##874
549##Divisibility of Factorials##2016-02-28 10:00:00##3647
550##Divisor Game##2016-03-05 13:00:00##527
551##Sum of Digits Sequence##2016-03-12 16:00:00##682
552##Chinese Leftovers II##2016-03-19 19:00:00##644
553##Power Sets of Power Sets##2016-03-26 22:00:00##365
554##Centaurs on a Chess Board##2016-04-03 00:00:00##398
555##McCarthy 91 Function##2016-04-10 03:00:00##995
556##Squarefree Gaussian Integers##2016-04-17 06:00:00##412
557##Cutting Triangles##2016-04-24 09:00:00##431
558##Irrational Base##2016-04-30 12:00:00##377
559##Permuted Matrices##2016-05-07 15:00:00##370
560##Coprime Nim##2016-05-14 18:00:00##516
561##Divisor Pairs##2016-05-21 21:00:00##1124
562##Maximal Perimeter##2016-05-29 00:00:00##310
563##Robot Welders##2016-06-05 03:00:00##506
564##Maximal Polygons##2016-06-12 06:00:00##374
565##Divisibility of Sum of Divisors##2016-06-19 09:00:00##863
566##Cake Icing Puzzle##2016-06-25 12:00:00##469
567##Reciprocal Games I##2016-09-03 15:00:00##454
568##Reciprocal Games II##2016-09-03 15:00:00##436
569##Prime Mountain Range##2016-09-10 18:00:00##571
570##Snowflakes##2016-09-17 21:00:00##402
571##Super Pandigital Numbers##2016-09-25 00:00:00##1544
572##Idempotent Matrices##2016-10-02 03:00:00##510
573##Unfair Race##2016-10-09 06:00:00##351
574##Verifying Primes##2016-10-16 09:00:00##401
575##Wandering Robots##2016-10-22 12:00:00##816
576##Irrational Jumps##2016-10-29 15:00:00##344
577##Counting Hexagons##2016-11-12 19:00:00##2092
578##Integers with Decreasing Prime Powers##2016-11-19 22:00:00##395
579##Lattice Points in Lattice Cubes##2016-11-27 01:00:00##396
580##Squarefree Hilbert Numbers##2016-12-04 04:00:00##406
581##$47$-smooth Triangular Numbers##2016-12-11 07:00:00##1195
582##Nearly Isosceles $120$ Degree Triangles##2016-12-18 10:00:00##491
583##Heron Envelopes##2016-12-24 13:00:00##547
584##Birthday Problem Revisited##2016-12-31 16:00:00##419
585##Nested Square Roots##2017-01-07 19:00:00##418
586##Binary Quadratic Form##2017-01-14 22:00:00##372
587##Concave Triangle##2017-01-22 01:00:00##4257
588##Quintinomial Coefficients##2017-01-29 04:00:00##626
589##Poohsticks Marathon##2017-02-05 07:00:00##341
590##Sets with a Given Least Common Multiple##2017-02-12 10:00:00##401
591##Best Approximations by Quadratic Integers##2017-02-18 13:00:00##356
592##Factorial Trailing Digits 2##2017-02-25 16:00:00##451
593##Fleeting Medians##2017-03-04 19:00:00##785
594##Rhombus Tilings##2017-03-11 22:00:00##312
595##Incremental Random Sort##2017-03-19 01:00:00##908
596##Number of Lattice Points in a Hyperball##2017-03-26 03:00:00##545
597##Torpids##2017-04-02 06:00:00##482
598##Split Divisibilities##2017-04-09 09:00:00##699
599##Distinct Colourings of a Rubik's Cube##2017-04-15 12:00:00##474
600##Integer Sided Equiangular Hexagons##2017-04-22 15:00:00##855
601##Divisibility Streaks##2017-04-29 18:00:00##2771
602##Product of Head Counts##2017-05-06 21:00:00##722
603##Substring Sums of Prime Concatenations##2017-05-14 00:00:00##609
604##Convex Path in Square##2017-05-21 03:00:00##725
605##Pairwise Coin-Tossing Game##2017-05-28 06:00:00##1157
606##Gozinta Chains II##2017-06-04 09:00:00##544
607##Marsh Crossing##2017-06-10 12:00:00##2212
608##Divisor Sums##2017-06-17 15:00:00##484
609##$\pi$ Sequences##2017-09-09 15:00:00##1230
610##Roman Numerals II##2017-09-23 18:00:00##865
611##Hallway of Square Steps##2017-10-07 21:00:00##478
612##Friend Numbers##2017-10-22 00:00:00##978
613##Pythagorean Ant##2017-11-05 04:00:00##2333
614##Special Partitions 2##2017-11-19 07:00:00##465
615##The Millionth Number with at Least One Million Prime Factors##2017-12-03 10:00:00##826
616##Creative Numbers##2017-12-16 13:00:00##663
617##Mirror Power Sequence##2017-12-30 16:00:00##520
618##Numbers with a Given Prime Factor Sum##2018-01-13 19:00:00##1402
619##Square Subsets##2018-01-27 22:00:00##613
620##Planetary Gears##2018-02-11 01:00:00##285
621##Expressing an Integer as the Sum of Triangular Numbers##2018-02-25 04:00:00##778
622##Riffle Shuffles##2018-03-11 07:00:00##2210
623##Lambda Count##2018-03-25 09:00:00##482
624##Two Heads Are Better Than One##2018-04-07 12:00:00##885
625##Gcd Sum##2018-04-21 15:00:00##972
626##Counting Binary Matrices##2018-05-05 18:00:00##383
627##Counting Products##2018-05-19 21:00:00##375
628##Open Chess Positions##2018-06-03 00:00:00##1114
629##Scatterstone Nim##2018-06-17 03:00:00##363
630##Crossed Lines##2018-07-01 06:00:00##1405
631##Constrained Permutations##2018-07-15 09:00:00##290
632##Square Prime Factors##2018-07-28 12:00:00##712
633##Square Prime Factors II##2018-07-28 12:00:00##481
634##Numbers of the Form $a^2b^3$##2018-08-11 15:00:00##871
635##Subset Sums##2018-08-25 18:00:00##570
636##Restricted Factorisations##2018-09-08 21:00:00##347
637##Flexible Digit Sum##2018-09-23 00:00:00##488
638##Weighted Lattice Paths##2018-10-07 03:00:00##551
639##Summing a Multiplicative Function##2018-10-21 06:00:00##442
640##Shut the Box##2018-10-28 10:00:00##525
641##A Long Row of Dice##2018-11-03 13:00:00##705
642##Sum of Largest Prime Factors##2018-11-10 16:00:00##539
643##$2$-Friendly##2018-11-17 19:00:00##926
644##Squares on the Line##2018-11-24 22:00:00##291
645##Every Day Is a Holiday##2018-12-02 01:00:00##366
646##Bounded Divisors##2018-12-09 04:00:00##434
647##Linear Transformations of Polygonal Numbers##2018-12-16 07:00:00##629
648##Skipping Squares##2018-12-23 10:00:00##429
649##Low-Prime Chessboard Nim##2018-12-29 13:00:00##625
650##Divisors of Binomial Product##2019-01-05 16:00:00##2285
651##Patterned Cylinders##2019-01-12 19:00:00##293
652##Distinct Values of a Proto-logarithmic Function##2019-01-19 22:00:00##269
653##Frictionless Tube##2019-01-27 01:00:00##467
654##Neighbourly Constraints##2019-02-03 04:00:00##504
655##Divisible Palindromes##2019-02-10 07:00:00##801
656##Palindromic Sequences##2019-02-17 10:00:00##355
657##Incomplete Words##2019-02-23 13:00:00##811
658##Incomplete Words II##2019-02-23 13:00:00##359
659##Largest Prime##2019-03-02 16:00:00##1350
660##Pandigital Triangles##2019-03-09 19:00:00##451
661##A Long Chess Match##2019-03-16 22:00:00##354
662##Fibonacci Paths##2019-03-24 01:00:00##1140
663##Sums of Subarrays##2019-03-31 03:00:00##524
664##An Infinite Game##2019-04-07 06:00:00##305
665##Proportionate Nim##2019-04-14 09:00:00##367
666##Polymorphic Bacteria##2019-04-20 12:00:00##461
667##Moving Pentagon##2019-04-27 15:00:00##334
668##Square Root Smooth Numbers##2019-05-04 18:00:00##1393
669##The King's Banquet##2019-05-11 21:00:00##462
670##Colouring a Strip##2019-05-19 00:00:00##528
671##Colouring a Loop##2019-05-19 00:00:00##287
672##One More One##2019-05-26 03:00:00##398
673##Beds and Desks##2019-06-02 06:00:00##491
674##Solving $\mathcal{I}$-equations##2019-06-09 09:00:00##279
675##$2^{\omega(n)}$##2019-06-15 12:00:00##1107
676##Matching Digit Sums##2019-06-22 15:00:00##343
677##Coloured Graphs##2019-06-29 18:00:00##329
678##Fermat-like Equations##2019-09-07 21:00:00##372
679##Freefarea##2019-09-15 00:00:00##1341
680##Yarra Gnisrever##2019-09-22 03:00:00##316
681##Maximal Area##2019-09-29 06:00:00##351
682##$5$-Smooth Pairs##2019-10-06 09:00:00##403
683##The Chase II##2019-10-12 12:00:00##462
684##Inverse Digit Sum##2019-10-19 15:00:00##3554
685##Inverse Digit Sum II##2019-10-19 15:00:00##300
686##Powers of Two##2019-10-26 18:00:00##4895
687##Shuffling Cards##2019-11-02 22:00:00##457
688##Piles of Plates##2019-11-10 01:00:00##1069
689##Binary Series##2019-11-17 04:00:00##375
690##Tom and Jerry##2019-11-24 07:00:00##325
691##Long Substring with Many Repetitions##2019-12-01 10:00:00##405
692##Siegbert and Jo##2019-12-07 13:00:00##1950
693##Finite Sequence Generator##2019-12-14 16:00:00##394
694##Cube-full Divisors##2019-12-21 19:00:00##1418
695##Random Rectangles##2019-12-28 22:00:00##342
696##Mahjong##2020-01-05 01:00:00##379
697##Randomly Decaying Sequence##2020-01-12 04:00:00##827
698##123 Numbers##2020-01-19 07:00:00##660
699##Triffle Numbers##2020-01-26 10:00:00##293
700##Eulercoin##2020-02-01 13:00:00##4738
701##Random Connected Area##2020-02-08 16:00:00##548
702##Jumping Flea##2020-02-15 19:00:00##300
703##Circular Logic II##2020-02-22 22:00:00##478
704##Factors of Two in Binomial Coefficients##2020-03-01 01:00:00##1451
705##Total Inversion Count of Divided Sequences##2020-03-08 04:00:00##679
706##$3$-Like Numbers##2020-03-15 07:00:00##869
707##Lights Out##2020-03-22 10:00:00##367
708##Twos Are All You Need##2020-03-28 13:00:00##512
709##Even Stevens##2020-04-04 16:00:00##1247
710##One Million Members##2020-04-11 19:00:00##1814
711##Binary Blackboard##2020-04-11 19:00:00##510
712##Exponent Difference##2020-04-18 22:00:00##710
713##Turán's Water Heating System##2020-04-26 01:00:00##1052
714##Duodigits##2020-05-03 04:00:00##996
715##Sextuplet Norms##2020-05-10 07:00:00##310
716##Grid Graphs##2020-05-17 10:00:00##356
717##Summation of a Modular Formula##2020-05-23 13:00:00##761
718##Unreachable Numbers##2020-05-30 16:00:00##495
719##Number Splitting##2020-06-06 19:00:00##5716
720##Unpredictable Permutations##2020-06-13 22:00:00##443
721##High Powers of Irrational Numbers##2020-06-21 01:00:00##631
722##Slowly Converging Series##2020-06-28 04:00:00##727
723##Pythagorean Quadrilaterals##2020-07-05 07:00:00##289
724##Drone Delivery##2020-09-05 13:00:00##608
725##Digit Sum Numbers##2020-09-12 16:00:00##1597
726##Falling Bottles##2020-09-19 19:00:00##302
727##Triangle of Circular Arcs##2020-09-26 22:00:00##741
728##Circle of Coins##2020-10-04 01:00:00##432
729##Range of Periodic Sequence##2020-10-11 04:00:00##375
730##Shifted Pythagorean Triples##2020-10-18 07:00:00##278
731##A Stoneham Number##2020-10-25 10:00:00##819
732##Standing on the Shoulders of Trolls##2020-10-31 13:00:00##337
733##Ascending Subsequences##2020-11-07 16:00:00##682
734##A Bit of Prime##2020-11-14 19:00:00##517
735##Divisors of $2n^2$##2020-11-21 22:00:00##360
736##Paths to Equality##2020-11-29 01:00:00##342
737##Coin Loops##2020-12-06 04:00:00##551
738##Counting Ordered Factorisations##2020-12-13 07:00:00##419
739##Summation of Summations##2020-12-20 10:00:00##774
740##Secret Santa##2020-12-26 13:00:00##308
741##Binary Grid Colouring##2021-01-02 16:00:00##273
742##Minimum Area of a Convex Grid Polygon##2021-01-09 19:00:00##261
743##Window into a Matrix##2021-01-16 22:00:00##1729
744##What? Where? When?##2021-01-24 01:00:00##458
745##Sum of Squares II##2021-01-31 04:00:00##1813
746##A Messy Dinner##2021-02-07 07:00:00##433
747##Triangular Pizza##2021-02-14 10:00:00##312
748##Upside Down Diophantine Equation##2021-02-20 13:00:00##447
749##Near Power Sums##2021-02-27 16:00:00##1033
750##Optimal Card Stacking##2021-03-06 19:00:00##476
751##Concatenation Coincidence##2021-03-13 22:00:00##3277
752##Powers of $1+\sqrt 7$##2021-03-21 01:00:00##960
753##Fermat Equation##2021-03-28 04:00:00##599
754##Product of Gauss Factorials##2021-04-04 07:00:00##998
755##Not Zeckendorf##2021-04-18 10:00:00##1303
756##Approximating a Sum##2021-05-01 13:00:00##484
757##Stealthy Numbers##2021-05-15 16:00:00##1852
758##Buckets of Water##2021-05-29 19:00:00##341
759##A Squared Recurrence Relation##2021-06-12 22:00:00##815
760##Sum over Bitwise Operators##2021-06-27 01:00:00##630
761##Runner and Swimmer##2021-07-11 04:00:00##334
762##Amoebas in a 2D Grid##2021-09-04 13:00:00##352
763##Amoebas in a 3D Grid##2021-09-04 13:00:00##387
764##Asymmetric Diophantine Equation##2021-09-11 16:00:00##575
765##Trillionaire##2021-09-18 19:00:00##336
766##Sliding Block Puzzle##2021-10-02 22:00:00##494
767##Window into a Matrix II##2021-10-10 01:00:00##281
768##Chandelier##2021-10-17 04:00:00##323
769##Binary Quadratic Form II##2021-10-24 06:00:00##258
770##Delphi Flip##2021-10-31 10:00:00##765
771##Pseudo Geometric Sequences##2021-11-06 13:00:00##220
772##Balanceable $k$-bounded Partitions##2021-11-13 16:00:00##807
773##Ruff Numbers##2021-11-20 19:00:00##311
774##Conjunctive Sequences##2021-11-27 22:00:00##246
775##Saving Paper##2021-12-05 01:00:00##369
776##Digit Sum Division##2021-12-12 04:00:00##793
777##Lissajous Curves##2021-12-19 07:00:00##232
778##Freshman's Product##2021-12-26 10:00:00##635
779##Prime Factor and Exponent##2022-01-01 13:00:00##717
780##Toriangulations##2022-01-08 16:00:00##311
781##Feynman Diagrams##2022-01-15 19:00:00##239
782##Distinct Rows and Columns##2022-01-22 22:00:00##258
783##Urns##2022-01-30 01:00:00##290
784##Reciprocal Pairs##2022-02-06 04:00:00##602
785##Symmetric Diophantine Equation##2022-02-13 07:00:00##311
786##Billiard##2022-02-20 10:00:00##257
787##Bézout's Game##2022-02-26 13:00:00##308
788##Dominating Numbers##2022-03-05 16:00:00##1850
789##Minimal Pairing Modulo $p$##2022-03-12 19:00:00##317
790##Clock Grid##2022-03-19 22:00:00##393
791##Average and Variance##2022-03-27 01:00:00##264
792##Too Many Twos##2022-04-03 04:00:00##312
793##Median of Products##2022-04-10 07:00:00##976
794##Seventeen Points##2022-04-17 10:00:00##479
795##Alternating GCD Sum##2022-04-23 13:00:00##555
796##A Grand Shuffle##2022-04-30 16:00:00##328
797##Cyclogenic Polynomials##2022-05-07 19:00:00##310
798##Card Stacking Game##2022-05-14 22:00:00##266
799##Pentagonal Puzzle##2022-05-22 01:00:00##344
800##Hybrid Integers##2022-05-29 04:00:00##2897
801##$x^y \equiv y^x$##2022-06-05 07:00:00##467
802##Iterated Composition##2022-06-12 10:00:00##406
803##Pseudorandom Sequence##2022-06-18 13:00:00##340
804##Counting Binary Quadratic Representations##2022-06-25 16:00:00##981
805##Shifted Multiples##2022-07-02 19:00:00##279
806##Nim on Towers of Hanoi##2022-07-09 22:00:00##259
807##Loops of Ropes##2022-09-11 01:00:00##230
808##Reversible Prime Squares##2022-09-18 04:00:00##4332
809##Rational Recurrence Relation ##2022-09-25 07:00:00##443
810##XOR-Primes##2022-10-02 10:00:00##1030
811##Bitwise Recursion##2022-10-08 13:00:00##358
812##Dynamical Polynomials##2022-10-15 16:00:00##285
813##XOR-Powers##2022-10-22 19:00:00##823
814##Mezzo-forte##2022-10-29 22:00:00##341
815##Group by Value##2022-11-06 01:00:00##612
816##Shortest Distance Among Points##2022-11-13 04:00:00##3204
817##Digits in Squares##2022-11-20 07:00:00##653
818##SET##2022-11-27 10:00:00##246
819##Iterative Sampling##2022-12-03 13:00:00##348
820##$N$<sup>th</sup> Digit of Reciprocals##2022-12-10 16:00:00##1672
821##123-Separable##2022-12-17 19:00:00##257
822##Square the Smallest##2022-12-24 22:00:00##1196
823##Factor Shuffle##2023-01-01 01:00:00##293
824##Chess Sliders##2023-01-08 04:00:00##257
825##Chasing Game##2023-01-15 07:00:00##246
826##Birds on a Wire##2023-01-22 10:00:00##393
827##Pythagorean Triple Occurrence##2023-01-28 13:00:00##279
828##Numbers Challenge##2023-02-04 16:00:00##943
829##Integral Fusion##2023-02-11 19:00:00##308
830##Binomials and Powers##2023-02-18 22:00:00##274
831##Triple Product##2023-02-26 01:00:00##301
832##Mex Sequence##2023-03-05 04:00:00##489
833##Square Triangle Products##2023-03-12 07:00:00##261
834##Add and Divide##2023-03-19 10:00:00##616
835##Supernatural Triangles##2023-03-25 13:00:00##563
836##A Bold Proposition##2023-04-01 16:00:00##7363
837##Amidakuji##2023-04-01 16:00:00##316
838##Not Coprime##2023-04-08 19:00:00##824
839##Beans in Bowls##2023-04-15 22:00:00##526
840##Sum of Products##2023-04-23 01:00:00##560
841##Regular Star Polygons##2023-04-30 04:00:00##273
842##Irregular Star Polygons##2023-05-07 07:00:00##211
843##Periodic Circles##2023-05-14 10:00:00##222
844##$k$-Markov Numbers##2023-05-20 13:00:00##318
845##Prime Digit Sum##2023-05-27 16:00:00##1279
846##Magic Bracelets##2023-06-03 19:00:00##312
847##Jack's Bean##2023-06-10 22:00:00##201
848##Guessing with Sets##2023-06-18 01:00:00##304
849##The Tournament##2023-06-25 04:00:00##378
850##Fractions of Powers##2023-07-02 07:00:00##228
851##SOP and POS##2023-07-09 10:00:00##270
852##Coins in a Box##2023-09-02 13:00:00##345
853##Pisano Periods 1##2023-09-09 16:00:00##1984
854##Pisano Periods 2##2023-09-09 16:00:00##503
855##Delphi Paper##2023-09-16 19:00:00##223
856##Waiting for a Pair##2023-09-23 22:00:00##884
857##Beautiful Graphs##2023-10-01 01:00:00##274
858##LCM##2023-10-08 04:00:00##350
859##Cookie Game##2023-10-15 07:00:00##331
860##Gold and Silver Coin Game##2023-10-22 10:00:00##708
861##Products of Bi-Unitary Divisors##2023-10-28 13:00:00##307
862##Larger Digit Permutation##2023-11-04 16:00:00##1170
863##Different Dice##2023-11-11 19:00:00##339
864##Square + 1 = Squarefree##2023-11-18 22:00:00##291
865##Triplicate Numbers##2023-11-26 01:00:00##403
866##Tidying Up B##2023-12-03 04:00:00##649
867##Tiling Dodecagon##2023-12-10 07:00:00##245
868##Belfry Maths##2023-12-17 10:00:00##686
869##Prime Guessing##2023-12-23 13:00:00##1044
870##Stone Game IV##2023-12-30 16:00:00##223
871##Drifting Subsets##2024-01-06 19:00:00##482
872##Recursive Tree##2024-01-13 22:00:00##1584
873##Words with Gaps##2024-01-21 01:00:00##477
874##Maximal Prime Score##2024-01-28 04:00:00##708
875##Quadruple Congruence##2024-02-04 07:00:00##320
876##Triplet Tricks##2024-02-11 10:00:00##200
877##XOR-Equation A##2024-02-17 13:00:00##642
878##XOR-Equation B##2024-02-17 13:00:00##378
879##Touch-screen Password##2024-02-24 16:00:00##618
880##Nested Radicals##2024-03-02 19:00:00##190
881##Divisor Graph Width##2024-03-09 22:00:00##698
882##Removing Bits##2024-03-17 01:00:00##305
883##Remarkable Triangles##2024-03-24 04:00:00##190
884##Removing Cubes##2024-03-31 07:00:00##810
885##Sorted Digits##2024-04-07 10:00:00##1424
886##Coprime Permutations##2024-04-13 13:00:00##397
887##Bounded Binary Search##2024-04-20 16:00:00##393
888##1249 Nim##2024-04-27 19:00:00##282
889##Rational Blancmange##2024-05-04 22:00:00##197
890##Binary Partitions##2024-05-12 01:00:00##326
891##Ambiguous Clock##2024-05-19 04:00:00##243
892##Zebra Circles##2024-05-26 07:00:00##231
893##Matchsticks##2024-06-02 10:00:00##833
894##Spiral of Circles##2024-06-08 13:00:00##460
895##Gold &amp; Silver Coin Game II##2024-06-15 16:00:00##195
896##Divisible Ranges##2024-06-22 19:00:00##307
897##Maximal $n$-gon in a region##2024-06-29 22:00:00##568
898##Claire Voyant##2024-07-07 01:00:00##434
899##DistribuNim I##2024-07-14 04:00:00##774
900##DistribuNim II##2024-07-14 04:00:00##230
901##Well Drilling##2024-07-21 07:00:00##694
902##Permutation Powers##2024-07-28 10:00:00##266
903##Total Permutation Powers##2024-07-28 10:00:00##237
904##Pythagorean Angle##2024-08-24 13:00:00##319
905##Now I Know##2024-08-31 16:00:00##472
906##A Collective Decision##2024-09-07 19:00:00##342
907##Stacking Cups##2024-09-14 22:00:00##402
908##Clock Sequence II##2024-09-22 01:00:00##228
909##L-expressions I##2024-09-29 04:00:00##295
910##L-expressions II##2024-09-29 04:00:00##208
911##Khinchin Exceptions##2024-10-06 07:00:00##269
912##Where are the Odds?##2024-10-13 10:00:00##294
913##Row-major vs Column-major##2024-10-19 13:00:00##243
914##Triangles inside Circles##2024-10-26 16:00:00##709
915##Giant GCDs##2024-11-02 19:00:00##327
916##Restricted Permutations##2024-11-09 22:00:00##261
917##Minimal Path Using Additive Cost##2024-11-17 01:00:00##314
918##Recursive Sequence Summation##2024-11-24 04:00:00##1753
919##Fortunate Triangles##2024-12-01 07:00:00##360
920##Tau Numbers##2024-12-08 10:00:00##399
921##Golden Recurrence##2024-12-14 13:00:00##305
922##Young's Game A##2024-12-21 16:00:00##203
923##Young's Game B##2024-12-21 16:00:00##186
924##Larger Digit Permutation II##2024-12-28 19:00:00##286
925##Larger Digit Permutation III##2024-12-28 19:00:00##241
926##Total Roundness##2025-01-04 22:00:00##958
927##Prime-ary Tree##2025-01-12 01:00:00##254
928##Cribbage##2025-01-19 04:00:00##324
929##Odd-Run Compositions##2025-01-26 07:00:00##328
930##The Gathering##2025-02-02 10:00:00##216
931##Totient Graph##2025-02-08 13:00:00##232
932##$2025$##2025-02-15 16:00:00##2411
933##Paper Cutting##2025-02-22 19:00:00##226
934##Unlucky Primes##2025-03-01 22:00:00##562
935##Rolling Square##2025-03-09 01:00:00##184
936##Peerless Trees##2025-03-16 04:00:00##192
937##Equiproduct Partition##2025-03-23 07:00:00##231
938##Exhausting a Colour##2025-03-30 10:00:00##1512
939##Partisan Nim##2025-04-05 13:00:00##202
940##Two-Dimensional Recurrence##2025-04-12 16:00:00##792
941##de Bruijn's Combination Lock##2025-04-19 19:00:00##187
942##Mersenne's Square Root##2025-04-26 22:00:00##232
943##Self Describing Sequences##2025-05-04 01:00:00##185
944##Sum of Elevisors##2025-05-11 04:00:00##1036
945##XOR-Equation C##2025-05-18 07:00:00##282
946##Continued Fraction Fraction##2025-05-25 10:00:00##376
947##Fibonacci Residues##2025-05-31 13:00:00##233
948##Left vs Right##2025-06-07 16:00:00##496
949##Left vs Right II##2025-06-07 16:00:00##237
950##Pirate Treasure##2025-06-14 19:00:00##199
951##A Game of Chance##2025-06-21 22:00:00##547
952##Order Modulo Factorial##2025-06-29 01:00:00##402
953##Factorisation Nim##2025-07-06 04:00:00##299
954##Heptaphobia##2025-07-13 07:00:00##268
955##Finding Triangles##2025-07-20 10:00:00##822
956##Super Duper Sum##2025-07-26 13:00:00##620
957##Point Genesis##2025-08-02 16:00:00##255
958##Euclid's Labour##2025-08-30 19:00:00##289
959##Asymmetric Random Walk##2025-09-06 22:00:00##369
960##Stone Game Solitaire##2025-09-14 01:00:00##263
961##Removing Digits##2025-09-21 04:00:00##1190
962##Angular Bisector and Tangent 2##2025-09-28 07:00:00##188
963##Removing Trits##2025-10-05 10:00:00##208
964##Musical Chairs Revisited##2025-10-11 13:00:00##249
965##Expected Minimal Fractional Value##2025-10-18 16:00:00##726
966##Triangle Circle Intersection##2025-10-25 19:00:00##215
967##$B$-Trivisible Numbers##2025-11-01 22:00:00##315
968##5D Summation##2025-11-09 01:00:00##194
969##Kangaroo Hopping##2025-11-16 04:00:00##378
970##Kangaroo Hopping over Sixes##2025-11-16 04:00:00##246
971##Modular Polynomial Composition##2025-11-23 07:00:00##281
972##Hyperbolic Plane##2025-11-30 10:00:00##296
973##Random Dealings##2025-12-06 13:00:00##195
974##Very Odd Numbers##2025-12-13 16:00:00##639
975##A Winding Path##2025-12-20 19:00:00##196
976##XO Game##2025-12-27 22:00:00##185
977##Iterated Functions##2026-01-04 01:00:00##239
978##Random Walk Skewness##2026-01-11 04:00:00##557
979##Heptagon Hopping##2026-01-18 07:00:00##302
980##The Quaternion Group I##2026-01-25 10:00:00##505
981##The Quaternion Group II##2026-01-25 10:00:00##317
982##The Third Dice##2026-01-31 13:00:00##240
983##Consonant Circle Crossing##2026-02-07 16:00:00##248
984##Knights and Horses##2026-02-14 19:00:00##184
985##Telescoping Triangles##2026-02-21 22:00:00##485
986##Another Infinite Game##2026-03-01 01:00:00##183
987##Straight Eight##2026-03-08 04:00:00##240
988##Non-attacking Frogs##2026-03-15 07:00:00##270
989##Fibonacci Sum##2026-03-22 10:00:00##188
990##Addition Equations##2026-03-28 13:00:00##200
991##Fruit Salad##2026-04-04 16:00:00##502
992##Another Frog Jumping##2026-04-11 19:00:00##252
993##Banana Beaver##2026-04-18 22:00:00##246
994##Counting Triangles##2026-04-26 01:00:00##189
995##A Particular Pair of Polynomials##2026-05-03 04:00:00##184
996##Overtakes##2026-05-10 07:00:00##184
997##Dice Box##2026-05-17 10:00:00##356
998##Squaring the Triangle##2026-05-23 13:00:00##183
999##Alternating Recurrence##2026-05-30 16:00:00##213
1000##Problem $1000$##2026-06-06 19:00:00##519
1001##Connections I##2026-06-13 22:00:00##252
1002##Connections II##2026-06-13 22:00:00##226
1003##Lonely Singles##2026-06-21 01:00:00##217
1004##Balanced Integer##2026-06-28 04:00:00##213
1005##Median Prime List##2026-07-05 07:00:00##668
1006##Fibonacci Subwords##2026-07-12 10:00:00##140
1007##Alternating Difference##2026-07-12 10:00:00##152
1008##Functional Inverse##2026-09-05 13:00:00##166
1009##A Change of Base##2026-09-12 16:00:00##177
1010##March of the Penguins##2026-09-19 19:00:00##105
1011##Modified Euclidean Algorithm##2026-09-26 22:00:00##275
1012##Rock Paper Scissors##2026-10-04 01:00:00##94
1013##Sum 25 Divisors##2026-10-05 17:00:00##608
1014##Steiner Club##2026-10-11 04:00:00##141
1015##Partisan Kayles##2026-10-18 07:00:00##88
1016##Squareful Matrix##2026-10-25 10:00:00##41