ID##Title##Published##Solved By
1##Multiples of 3 or 5##2001-10-05 17:00:00##861524
2##Even Fibonacci Numbers##2001-10-19 17:00:00##688521
3##Largest Prime Factor##2001-11-02 18:00:00##518071
4##Largest Palindrome Product##2001-11-16 18:00:00##457742
5##Smallest Multiple##2001-11-30 18:00:00##444152
6##Sum Square Difference##2001-12-14 18:00:00##449082
7##10 001st Prime##2001-12-28 18:00:00##391255
8##Largest Product in a Series##2002-01-11 18:00:00##332687
9##Special Pythagorean Triplet##2002-01-25 18:00:00##338443
10##Summation of Primes##2002-02-08 18:00:00##317587
11##Largest Product in a Grid##2002-02-22 18:00:00##237510
12##Highly Divisible Triangular Number##2002-03-08 18:00:00##233775
13##Large Sum##2002-03-22 18:00:00##234470
14##Longest Collatz Sequence##2002-04-05 17:00:00##238872
15##Lattice Paths##2002-04-19 17:00:00##202471
16##Power Digit Sum##2002-05-03 17:00:00##237044
17##Number Letter Counts##2002-05-17 17:00:00##169714
18##Maximum Path Sum I##2002-05-31 17:00:00##163952
19##Counting Sundays##2002-06-14 17:00:00##153789
20##Factorial Digit Sum##2002-06-21 17:00:00##207004
21##Amicable Numbers##2002-07-05 17:00:00##169072
22##Names Scores##2002-07-19 17:00:00##155757
23##Non-Abundant Sums##2002-08-02 17:00:00##128252
24##Lexicographic Permutations##2002-08-16 17:00:00##137468
25##$1000$-digit Fibonacci Number##2002-08-30 17:00:00##175362
26##Reciprocal Cycles##2002-09-13 17:00:00##104426
27##Quadratic Primes##2002-09-27 17:00:00##107939
28##Number Spiral Diagonals##2002-10-11 17:00:00##126652
29##Distinct Powers##2002-10-25 17:00:00##127687
30##Digit Fifth Powers##2002-11-08 18:00:00##132421
31##Coin Sums##2002-11-22 18:00:00##104275
32##Pandigital Products##2002-12-06 18:00:00##88828
33##Digit Cancelling Fractions##2002-12-20 18:00:00##88632
34##Digit Factorials##2003-01-03 18:00:00##114766
35##Circular Primes##2003-01-17 18:00:00##102871
36##Double-base Palindromes##2003-01-31 18:00:00##107340
37##Truncatable Primes##2003-02-14 18:00:00##90799
38##Pandigital Multiples##2003-02-28 18:00:00##78028
39##Integer Right Triangles##2003-03-14 18:00:00##89728
40##Champernowne's Constant##2003-03-28 18:00:00##96828
41##Pandigital Prime##2003-04-11 17:00:00##84174
42##Coded Triangle Numbers##2003-04-25 17:00:00##89709
43##Sub-string Divisibility##2003-05-09 17:00:00##74137
44##Pentagon Numbers##2003-05-23 17:00:00##72723
45##Triangular, Pentagonal, and Hexagonal##2003-06-06 17:00:00##86148
46##Goldbach's Other Conjecture##2003-06-20 17:00:00##76268
47##Distinct Primes Factors##2003-07-04 17:00:00##71754
48##Self Powers##2003-07-18 17:00:00##122957
49##Prime Permutations##2003-08-01 17:00:00##71363
50##Consecutive Prime Sum##2003-08-15 17:00:00##76456
51##Prime Digit Replacements##2003-08-29 17:00:00##43818
52##Permuted Multiples##2003-09-12 17:00:00##78683
53##Combinatoric Selections##2003-09-26 17:00:00##71288
54##Poker Hands##2003-10-10 17:00:00##44603
55##Lychrel Numbers##2003-10-24 17:00:00##65262
56##Powerful Digit Sum##2003-11-07 18:00:00##70510
57##Square Root Convergents##2003-11-21 18:00:00##51615
58##Spiral Primes##2003-12-05 18:00:00##49594
59##XOR Decryption##2003-12-19 18:00:00##49414
60##Prime Pair Sets##2004-01-02 18:00:00##34672
61##Cyclical Figurate Numbers##2004-01-16 18:00:00##32304
62##Cubic Permutations##2004-01-30 18:00:00##39840
63##Powerful Digit Counts##2004-02-13 18:00:00##52607
64##Odd Period Square Roots##2004-02-27 18:00:00##28006
65##Convergents of $e$##2004-03-12 18:00:00##37004
66##Diophantine Equation##2004-03-26 18:00:00##25208
67##Maximum Path Sum II##2004-04-09 17:00:00##106738
68##Magic 5-gon Ring##2004-04-23 17:00:00##26097
69##Totient Maximum##2004-05-07 17:00:00##43511
70##Totient Permutation##2004-05-21 17:00:00##28177
71##Ordered Fractions##2004-06-04 17:00:00##36173
72##Counting Fractions##2004-06-18 17:00:00##28138
73##Counting Fractions in a Range##2004-07-02 17:00:00##30992
74##Digit Factorial Chains##2004-07-16 17:00:00##33292
75##Singular Integer Right Triangles##2004-07-30 17:00:00##23002
76##Counting Summations##2004-08-13 17:00:00##35043
77##Prime Summations##2004-08-27 17:00:00##24423
78##Coin Partitions##2004-09-10 17:00:00##21901
79##Passcode Derivation##2004-09-17 17:00:00##46346
80##Square Root Digital Expansion##2004-10-08 17:00:00##24841
81##Path Sum: Two Ways##2004-10-22 17:00:00##41291
82##Path Sum: Three Ways##2004-11-05 18:00:00##26043
83##Path Sum: Four Ways##2004-11-19 18:00:00##22724
84##Monopoly Odds##2004-12-03 18:00:00##16193
85##Counting Rectangles##2004-12-17 18:00:00##30414
86##Cuboid Route##2005-01-07 18:00:00##16326
87##Prime Power Triples##2005-01-21 18:00:00##26045
88##Product-sum Numbers##2005-02-04 18:00:00##13410
89##Roman Numerals##2005-02-18 18:00:00##25600
90##Cube Digit Pairs##2005-03-04 18:00:00##14711
91##Right Triangles with Integer Coordinates##2005-03-18 18:00:00##19634
92##Square Digit Chains##2005-04-01 17:00:00##49384
93##Arithmetic Expressions##2005-04-15 17:00:00##15263
94##Almost Equilateral Triangles##2005-04-29 17:00:00##16214
95##Amicable Chains##2005-05-13 17:00:00##18460
96##Su Doku##2005-05-27 17:00:00##21143
97##Large Non-Mersenne Prime##2005-06-10 17:00:00##50081
98##Anagramic Squares##2005-06-17 17:00:00##14691
99##Largest Exponential##2005-07-01 17:00:00##37253
100##Arranged Probability##2005-07-15 17:00:00##20890
101##Optimum Polynomial##2005-07-29 17:00:00##15069
102##Triangle Containment##2005-08-12 17:00:00##26706
103##Special Subset Sums: Optimum##2005-08-26 17:00:00##10531
104##Pandigital Fibonacci Ends##2005-09-09 17:00:00##19892
105##Special Subset Sums: Testing##2005-09-23 17:00:00##10433
106##Special Subset Sums: Meta-testing##2005-10-07 17:00:00##8411
107##Minimal Network##2005-10-21 17:00:00##13546
108##Diophantine Reciprocals I##2005-11-04 18:00:00##15705
109##Darts##2005-11-18 18:00:00##10457
110##Diophantine Reciprocals II##2005-12-02 18:00:00##10421
111##Primes with Runs##2005-12-16 18:00:00##9410
112##Bouncy Numbers##2005-12-30 18:00:00##29922
113##Non-bouncy Numbers##2006-02-10 18:00:00##13670
114##Counting Block Combinations I##2006-02-17 18:00:00##13612
115##Counting Block Combinations II##2006-02-24 18:00:00##12467
116##Red, Green or Blue Tiles##2006-03-03 18:00:00##15030
117##Red, Green, and Blue Tiles##2006-03-10 18:00:00##13953
118##Pandigital Prime Sets##2006-03-24 18:00:00##9064
119##Digit Power Sum##2006-04-07 17:00:00##15269
120##Square Remainders##2006-04-21 17:00:00##16917
121##Disc Game Prize Fund##2006-05-19 17:00:00##12122
122##Efficient Exponentiation##2006-06-02 17:00:00##9880
123##Prime Square Remainders##2006-06-16 17:00:00##14149
124##Ordered Radicals##2006-07-14 17:00:00##16646
125##Palindromic Sums##2006-08-04 17:00:00##16589
126##Cuboid Layers##2006-08-18 17:00:00##6251
127##abc-hits##2006-09-01 17:00:00##8097
128##Hexagonal Tile Differences##2006-09-29 17:00:00##6523
129##Repunit Divisibility##2006-10-27 17:00:00##8050
130##Composites with Prime Repunit Property##2006-10-27 17:00:00##7568
131##Prime Cube Partnership##2006-11-10 18:00:00##9348
132##Large Repunit Factors##2006-12-01 18:00:00##8108
133##Repunit Nonfactors##2006-12-01 18:00:00##7164
134##Prime Pair Connection##2006-12-15 18:00:00##8965
135##Same Differences##2006-12-29 18:00:00##8221
136##Singleton Difference##2006-12-29 18:00:00##7331
137##Fibonacci Golden Nuggets##2007-01-12 18:00:00##7297
138##Special Isosceles Triangles##2007-01-20 11:00:00##7461
139##Pythagorean Tiles##2007-01-27 09:00:00##7296
140##Modified Fibonacci Golden Nuggets##2007-02-03 07:00:00##5761
141##Square Progressive Numbers##2007-02-17 05:00:00##5311
142##Perfect Square Collection##2007-02-24 01:00:00##7354
143##Torricelli Triangles##2007-03-02 21:00:00##3785
144##Laser Beam Reflections ##2007-03-09 17:00:00##7942
145##Reversible Numbers##2007-03-16 13:00:00##19973
146##Investigating a Prime Pattern ##2007-03-24 09:00:00##6649
147##Rectangles in Cross-hatched Grids##2007-03-31 05:00:00##4065
148##Exploring Pascal's Triangle##2007-04-07 01:00:00##6538
149##Maximum-sum Subsequence##2007-04-13 21:00:00##6182
150##Sub-triangle Sums##2007-04-13 21:00:00##5118
151##A Preference for A5##2007-04-20 17:00:00##7059
152##Sums of Square Reciprocals##2007-04-27 13:00:00##3663
153##Investigating Gaussian Integers##2007-05-05 09:00:00##3569
154##Exploring Pascal's Pyramid##2007-05-12 05:00:00##3539
155##Counting Capacitor Circuits##2007-05-19 01:00:00##4735
156##Counting Digits##2007-05-25 21:00:00##3368
157##Base-10 Diophantine Reciprocal##2007-06-01 17:00:00##3650
158##Lexicographical Neighbours##2007-06-15 13:00:00##4729
159##Digital Root Sums of Factorisations##2007-06-30 13:00:00##4327
160##Factorial Trailing Digits##2007-09-07 13:00:00##4624
161##Triominoes##2007-09-21 17:00:00##2956
162##Hexadecimal Numbers##2007-10-05 21:00:00##6652
163##Cross-hatched Triangles##2007-10-13 01:00:00##2558
164##Three Consecutive Digital Sum Limit##2007-10-20 05:00:00##7311
165##Intersections##2007-10-27 09:00:00##3512
166##Criss Cross##2007-11-03 13:00:00##5291
167##Investigating Ulam Sequences##2007-11-09 13:00:00##2400
168##Number Rotations##2007-11-16 17:00:00##3520
169##Sums of Powers of Two##2007-11-23 21:00:00##6504
170##Pandigital Concatenating Products##2007-12-01 01:00:00##2726
171##Square Sum of the Digital Squares##2007-12-08 05:00:00##3743
172##Few Repeated Digits##2007-12-15 09:00:00##4939
173##Hollow Square Laminae I##2007-12-22 13:00:00##11088
174##Hollow Square Laminae II##2007-12-22 13:00:00##7385
175##Fractions and Sum of Powers of Two##2007-12-28 13:00:00##2494
176##Common Cathetus Right-angled Triangles##2008-01-04 17:00:00##2603
177##Integer Angled Quadrilaterals##2008-01-11 21:00:00##1886
178##Step Numbers##2008-01-19 01:00:00##4424
179##Consecutive Positive Divisors##2008-01-26 05:00:00##13561
180##Golden Triplets##2008-02-02 09:00:00##2242
181##Grouping Two Different Coloured Objects##2008-02-09 13:00:00##2768
182##RSA Encryption##2008-02-15 13:00:00##3508
183##Maximum Product of Parts##2008-02-22 17:00:00##5852
184##Triangles Containing the Origin##2008-02-29 21:00:00##2299
185##Number Mind##2008-03-08 01:00:00##4047
186##Connectedness of a Network##2008-03-15 05:00:00##3792
187##Semiprimes##2008-03-22 09:00:00##13391
188##Hyperexponentiation##2008-04-04 13:00:00##7873
189##Tri-colouring a Triangular Grid##2008-04-11 16:00:00##2812
190##Maximising a Weighted Product##2008-04-18 21:00:00##5270
191##Prize Strings##2008-04-26 00:00:00##8670
192##Best Approximations##2008-05-03 04:00:00##2325
193##Squarefree Numbers##2008-05-10 12:00:00##4486
194##Coloured Configurations##2008-05-17 09:00:00##2017
195##$60$-degree Triangle Inscribed Circles##2008-05-23 13:00:00##2059
196##Prime Triplets##2008-05-30 17:00:00##3436
197##A Recursively Defined Sequence##2008-06-06 21:00:00##6066
198##Ambiguous Numbers##2008-06-14 01:00:00##1693
199##Iterative Circle Packing##2008-06-21 05:00:00##2650
200##Prime-proof Squbes##2008-06-28 09:00:00##3231
201##Subsets with a Unique Sum##2008-07-05 13:00:00##3169
202##Laserbeam##2008-07-05 13:00:00##3322
203##Squarefree Binomial Coefficients##2008-09-06 13:00:00##10906
204##Generalised Hamming Numbers##2008-09-06 13:00:00##8851
205##Dice Game##2008-09-06 13:00:00##17591
206##Concealed Square##2008-09-06 13:00:00##28489
207##Integer Partition Equations##2008-09-06 13:00:00##5763
208##Robot Walks##2008-09-12 13:00:00##2387
209##Circular Logic##2008-09-19 17:00:00##3261
210##Obtuse Angled Triangles##2008-09-26 21:00:00##2293
211##Divisor Square Sum##2008-10-04 01:00:00##5319
212##Combined Volume of Cuboids##2008-10-11 05:00:00##1909
213##Flea Circus##2008-10-18 09:00:00##3060
214##Totient Chains##2008-10-25 13:00:00##6447
215##Crack-free Walls##2008-10-31 13:00:00##4539
216##The Primality of $2n^2 - 1$##2008-11-07 17:00:00##5246
217##Balanced Numbers##2008-11-14 21:00:00##2094
218##Perfect Right-angled Triangles##2008-11-22 01:00:00##3755
219##Skew-cost Coding##2008-11-29 05:00:00##2000
220##Heighway Dragon##2008-12-06 09:00:00##2726
221##Alexandrian Integers##2008-12-13 13:00:00##2792
222##Sphere Packing##2008-12-19 13:00:00##2695
223##Almost Right-angled Triangles I##2008-12-26 17:00:00##2114
224##Almost Right-angled Triangles II##2008-12-26 17:00:00##1755
225##Tribonacci Non-divisors##2008-12-26 17:00:00##5485
226##A Scoop of Blancmange##2009-01-02 21:00:00##2311
227##The Chase##2009-01-10 01:00:00##2786
228##Minkowski Sums##2009-01-17 05:00:00##1844
229##Four Representations Using Squares##2009-01-24 09:00:00##1968
230##Fibonacci Words##2009-01-31 13:00:00##3537
231##Prime Factorisation of Binomial Coefficients##2009-02-06 13:00:00##6726
232##The Race##2009-02-13 17:00:00##2373
233##Lattice Points on a Circle##2009-02-20 21:00:00##3002
234##Semidivisible Numbers##2009-02-28 01:00:00##3991
235##An Arithmetic Geometric Sequence##2009-03-07 05:00:00##5950
236##Luxury Hampers##2009-03-14 09:00:00##1366
237##Tours on a $4 \times N$ Playing Board##2009-03-21 13:00:00##2147
238##Infinite String Tour##2009-03-29 14:00:00##1379
239##Twenty-two Foolish Primes##2009-04-03 16:00:00##2393
240##Top Dice##2009-04-10 21:00:00##2802
241##Perfection Quotients##2009-04-18 01:00:00##1381
242##Odd Triplets##2009-04-25 05:00:00##1499
243##Resilience##2009-05-02 09:00:00##11181
244##Sliders##2009-05-09 13:00:00##1792
245##Coresilience##2009-05-15 13:00:00##1260
246##Tangents to an Ellipse##2009-05-22 16:00:00##1248
247##Squares Under a Hyperbola##2009-05-29 20:00:00##2002
248##Euler's Totient Function Equals 13!##2009-06-06 00:00:00##1801
249##Prime Subset Sums##2009-06-13 04:00:00##3267
250##$250250$##2009-06-13 04:00:00##3911
251##Cardano Triplets##2009-06-20 08:00:00##1923
252##Convex Holes##2009-06-27 12:00:00##1238
253##Tidying Up A##2009-08-28 12:00:00##1473
254##Sums of Digit Factorials##2009-09-04 16:00:00##1378
255##Rounded Square Roots##2009-09-11 20:00:00##1257
256##Tatami-Free Rooms##2009-09-19 00:00:00##1112
257##Angular Bisectors##2009-09-26 04:00:00##1060
258##A Lagged Fibonacci Sequence##2009-10-03 08:00:00##2168
259##Reachable Numbers##2009-10-10 12:00:00##2017
260##Stone Game##2009-10-16 12:00:00##1766
261##Pivotal Square Sums##2009-10-23 16:00:00##1071
262##Mountain Range##2009-10-30 21:00:00##1077
263##An Engineers' Dream Come True##2009-11-07 01:00:00##1456
264##Triangle Centres##2009-11-14 05:00:00##912
265##Binary Circles##2009-11-21 09:00:00##5130
266##Pseudo Square Root##2009-11-28 13:00:00##2281
267##Billionaire##2009-12-04 13:00:00##4189
268##At Least Four Distinct Prime Factors Less Than 100##2009-12-11 17:00:00##1985
269##Polynomials with at Least One Integer Root##2009-12-19 09:00:00##1164
270##Cutting Squares##2009-12-26 01:00:00##968
271##Modular Cubes, Part 1##2010-01-02 05:00:00##3128
272##Modular Cubes, Part 2##2010-01-02 05:00:00##1425
273##Sum of Squares##2010-01-09 13:00:00##1883
274##Divisibility Multipliers##2010-01-15 13:00:00##1999
275##Balanced Sculptures##2010-01-22 17:00:00##933
276##Primitive Triangles##2010-01-29 21:00:00##1506
277##A Modified Collatz Sequence##2010-02-06 01:00:00##4064
278##Linear Combinations of Semiprimes##2010-02-13 05:00:00##1465
279##Triangles with Integral Sides and an Integral Angle ##2010-02-20 09:00:00##1101
280##Ant and Seeds##2010-02-27 13:00:00##1476
281##Pizza Toppings##2010-03-05 13:00:00##1425
282##The Ackermann Function##2010-03-12 17:00:00##1482
283##Integer Sided Triangles with Integral Area/perimeter Ratio##2010-03-19 21:00:00##958
284##Steady Squares##2010-03-27 01:00:00##1701
285##Pythagorean Odds##2010-04-03 04:00:00##1676
286##Scoring Probabilities##2010-04-03 04:00:00##2802
287##Quadtree Encoding (a Simple Compression Algorithm)##2010-04-10 08:00:00##1936
288##An Enormous Factorial##2010-04-17 12:00:00##2279
289##Eulerian Cycles##2010-04-23 12:00:00##835
290##Digital Signature##2010-04-30 16:00:00##1412
291##Panaitopol Primes##2010-05-07 20:00:00##1996
292##Pythagorean Polygons##2010-05-15 00:00:00##885
293##Pseudo-Fortunate Numbers##2010-05-22 04:00:00##3810
294##Sum of Digits - Experience #23##2010-05-29 08:00:00##1321
295##Lenticular Holes##2010-06-05 12:00:00##741
296##Angular Bisector and Tangent##2010-06-11 12:00:00##992
297##Zeckendorf Representation##2010-06-18 16:00:00##3571
298##Selective Amnesia##2010-06-25 20:00:00##994
299##Three Similar Triangles##2010-07-03 00:00:00##930
300##Protein Folding##2010-09-04 12:00:00##1512
301##Nim##2010-09-11 15:00:00##8080
302##Strong Achilles Numbers##2010-09-18 18:00:00##1122
303##Multiples with Small Digits##2010-09-25 21:00:00##4541
304##Primonacci##2010-10-03 00:00:00##2916
305##Reflexive Position##2010-10-10 03:00:00##911
306##Paper-strip Game##2010-10-17 06:00:00##1740
307##Chip Defects##2010-10-24 09:00:00##2198
308##An Amazing Prime-generating Automaton##2010-10-30 12:00:00##1111
309##Integer Ladders##2010-11-06 16:00:00##1208
310##Nim Square##2010-11-13 19:00:00##1657
311##Biclinic Integral Quadrilaterals##2010-11-20 22:00:00##696
312##Cyclic Paths on Sierpiński Graphs##2010-11-28 01:00:00##1224
313##Sliding Game##2010-12-05 04:00:00##2199
314##The Mouse on the Moon##2010-12-12 07:00:00##800
315##Digital Root Clocks##2010-12-19 10:00:00##4223
316##Numbers in Decimal Expansions##2010-12-25 13:00:00##981
317##Firecracker##2011-01-01 16:00:00##3407
318##2011 Nines##2011-01-01 16:00:00##1338
319##Bounded Sequences##2011-01-08 19:00:00##684
320##Factorials Divisible by a Huge Integer##2011-01-15 22:00:00##1284
321##Swapping Counters##2011-01-23 01:00:00##2267
322##Binomial Coefficients Divisible by 10##2011-01-30 04:00:00##731
323##Bitwise-OR Operations on Random Integers##2011-02-06 07:00:00##4852
324##Building a Tower##2011-02-13 10:00:00##1043
325##Stone Game II##2011-02-19 13:00:00##940
326##Modulo Summations##2011-02-26 16:00:00##826
327##Rooms of Doom##2011-03-05 19:00:00##1511
328##Lowest-cost Search##2011-03-12 22:00:00##738
329##Prime Frog##2011-03-20 01:00:00##3234
330##Euler's Number##2011-03-27 04:00:00##808
331##Cross Flips##2011-04-03 07:00:00##745
332##Spherical Triangles##2011-04-10 09:00:00##907
333##Special Partitions##2011-04-16 12:00:00##1693
334##Spilling the Beans##2011-04-23 15:00:00##743
335##Gathering the Beans##2011-04-23 15:00:00##797
336##Maximix Arrangements##2011-04-30 18:00:00##2680
337##Totient Stairstep Sequences##2011-05-07 21:00:00##818
338##Cutting Rectangular Grid Paper##2011-05-15 00:00:00##603
339##Peredur Fab Efrawg##2011-05-22 03:00:00##828
340##Crazy Function##2011-05-29 06:00:00##1571
341##Golomb's Self-describing Sequence##2011-06-05 09:00:00##1291
342##The Totient of a Square Is a Cube##2011-06-11 12:00:00##1132
343##Fractional Sequences##2011-06-18 15:00:00##1833
344##Silver Dollar Game##2011-06-25 18:00:00##618
345##Matrix Sum##2011-09-03 15:00:00##7143
346##Strong Repunits##2011-09-03 15:00:00##5601
347##Largest Integer Divisible by Two Primes##2011-09-03 15:00:00##5742
348##Sum of a Square and a Cube##2011-09-03 15:00:00##3982
349##Langton's Ant##2011-09-03 15:00:00##2497
350##Constraining the Least Greatest and the Greatest Least##2011-09-10 18:00:00##754
351##Hexagonal Orchards##2011-09-17 21:00:00##3322
352##Blood Tests##2011-10-02 00:00:00##893
353##Risky Moon##2011-10-09 03:00:00##775
354##Distances in a Bee's Honeycomb ##2011-10-16 06:00:00##703
355##Maximal Coprime Subset##2011-10-23 09:00:00##828
356##Largest Roots of Cubic Polynomials##2011-10-29 12:00:00##905
357##Prime Generating Integers##2011-11-05 16:00:00##9927
358##Cyclic Numbers##2011-11-12 19:00:00##2091
359##Hilbert's New Hotel##2011-11-19 22:00:00##1988
360##Scary Sphere##2011-11-27 01:00:00##831
361##Subsequence of Thue-Morse Sequence##2011-12-04 04:00:00##571
362##Squarefree Factors##2011-12-11 07:00:00##727
363##Bézier Curves##2011-12-18 10:00:00##1555
364##Comfortable Distance##2011-12-24 13:00:00##986
365##A Huge Binomial Coefficient##2011-12-31 16:00:00##1734
366##Stone Game III##2012-01-07 19:00:00##975
367##Bozo Sort##2012-01-14 22:00:00##780
368##A Kempner-like Series##2012-01-22 01:00:00##798
369##Badugi##2012-01-29 04:00:00##721
370##Geometric Triangles##2012-02-05 07:00:00##796
371##Licence Plates##2012-02-12 10:00:00##2165
372##Pencils of Rays##2012-02-18 13:00:00##619
373##Circumscribed Circles##2012-02-25 16:00:00##574
374##Maximum Integer Partition Product##2012-03-03 19:00:00##979
375##Minimum of Subsequences##2012-03-10 22:00:00##1216
376##Nontransitive Sets of Dice##2012-03-18 01:00:00##486
377##Sum of Digits - Experience #13##2012-03-25 04:00:00##1105
378##Triangle Triples##2012-04-01 06:00:00##1244
379##Least Common Multiple Count##2012-04-08 10:00:00##795
380##Amazing Mazes!##2012-04-14 13:00:00##766
381##$(\text{prime}-k)$ Factorial##2012-04-21 16:00:00##5582
382##Generating Polygons##2012-04-28 19:00:00##561
383##Divisibility Comparison Between Factorials##2012-05-05 22:00:00##731
384##Rudin-Shapiro Sequence##2012-05-13 01:00:00##519
385##Ellipses Inside Triangles##2012-05-20 04:00:00##498
386##Maximum Length of an Antichain##2012-05-27 07:00:00##1055
387##Harshad Numbers##2012-06-03 10:00:00##5793
388##Distinct Lines##2012-06-09 13:00:00##862
389##Platonic Dice##2012-06-16 16:00:00##1990
390##Triangles with Non Rational Sides and Integral Area##2012-06-23 19:00:00##801
391##Hopping Game##2012-06-30 22:00:00##475
392##Enmeshed Unit Circle##2012-09-01 13:00:00##1076
393##Migrating Ants##2012-09-08 16:00:00##1078
394##Eating Pie##2012-09-15 19:00:00##802
395##Pythagorean Tree##2012-09-22 22:00:00##977
396##Weak Goodstein Sequence##2012-09-30 01:00:00##920
397##Triangle on Parabola##2012-10-07 04:00:00##465
398##Cutting Rope##2012-10-14 07:00:00##613
399##Squarefree Fibonacci Numbers##2012-10-21 10:00:00##860
400##Fibonacci Tree Game##2012-10-27 13:00:00##715
401##Sum of Squares of Divisors##2012-11-10 16:00:00##3422
402##Integer-valued Polynomials##2012-11-17 19:00:00##656
403##Lattice Points Enclosed by Parabola and Line##2012-11-24 22:00:00##570
404##Crisscross Ellipses##2012-12-02 01:00:00##529
405##A Rectangular Tiling##2012-12-09 04:00:00##907
406##Guessing Game##2012-12-16 07:00:00##616
407##Idempotents##2012-12-23 10:00:00##3199
408##Admissible Paths Through a Grid##2012-12-29 13:00:00##842
409##Nim Extreme##2013-01-05 16:00:00##679
410##Circle and Tangent Line##2013-01-12 19:00:00##473
411##Uphill Paths##2013-01-19 22:00:00##970
412##Gnomon Numbering##2013-01-27 01:00:00##757
413##One-child Numbers##2013-02-03 04:00:00##629
414##Kaprekar Constant##2013-02-10 07:00:00##472
415##Titanic Sets##2013-02-17 10:00:00##624
416##A Frog's Trip##2013-02-23 13:00:00##501
417##Reciprocal Cycles II##2013-03-02 16:00:00##1315
418##Factorisation Triples##2013-03-09 19:00:00##964
419##Look and Say Sequence##2013-03-16 22:00:00##700
420##$2 \times 2$ Positive Integer Matrix##2013-03-24 01:00:00##681
421##Prime Factors of $n^{15}+1$##2013-03-31 03:00:00##956
422##Sequence of Points on a Hyperbola##2013-04-07 06:00:00##479
423##Consecutive Die Throws##2013-04-14 09:00:00##755
424##Kakuro##2013-04-20 12:00:00##614
425##Prime Connection##2013-04-27 15:00:00##1979
426##Box-Ball System##2013-05-04 18:00:00##429
427##$n$-sequences##2013-05-11 21:00:00##576
428##Necklace of Circles##2013-05-19 00:00:00##448
429##Sum of Squares of Unitary Divisors##2013-05-26 03:00:00##3291
430##Range Flips##2013-06-02 06:00:00##1130
431##Square Space Silo##2013-06-09 09:00:00##918
432##Totient Sum##2013-06-15 12:00:00##764
433##Steps in Euclid's Algorithm##2013-06-22 15:00:00##707
434##Rigid Graphs##2013-06-29 18:00:00##537
435##Polynomials of Fibonacci Numbers##2013-09-07 15:00:00##1562
436##Unfair Wager##2013-09-14 18:00:00##672
437##Fibonacci Primitive Roots##2013-09-21 21:00:00##1183
438##Integer Part of Polynomial Equation's Solutions##2013-09-29 00:00:00##472
439##Sum of Sum of Divisors##2013-10-06 03:00:00##689
440##GCD and Tiling##2013-10-13 06:00:00##601
441##The Inverse Summation of Coprime Couples##2013-10-20 09:00:00##572
442##Eleven-free Integers##2013-10-26 12:00:00##623
443##GCD Sequence##2013-11-02 16:00:00##1613
444##The Roundtable Lottery##2013-11-09 19:00:00##503
445##Retractions A##2013-11-16 22:00:00##621
446##Retractions B##2013-11-16 22:00:00##590
447##Retractions C##2013-11-16 22:00:00##564
448##Average Least Common Multiple##2013-11-24 01:00:00##565
449##Chocolate Covered Candy##2013-12-08 04:00:00##1246
450##Hypocycloid and Lattice Points##2013-12-15 07:00:00##395
451##Modular Inverses##2013-12-22 10:00:00##1984
452##Long Products##2013-12-28 13:00:00##871
453##Lattice Quadrilaterals##2014-01-04 16:00:00##434
454##Diophantine Reciprocals III##2014-01-11 19:00:00##722
455##Powers with Trailing Digits##2014-01-18 22:00:00##1034
456##Triangles Containing the Origin II##2014-01-26 01:00:00##613
457##A Polynomial Modulo the Square of a Prime##2014-02-02 04:00:00##1149
458##Permutations of Project##2014-02-09 07:00:00##1288
459##Flipping Game##2014-02-16 10:00:00##448
460##An Ant on the Move##2014-02-22 13:00:00##506
461##Almost Pi##2014-03-01 16:00:00##1635
462##Permutation of 3-smooth Numbers##2014-03-08 19:00:00##524
463##A Weird Recurrence Relation##2014-03-15 22:00:00##1509
464##Möbius Function and Intervals##2014-03-23 01:00:00##505
465##Polar Polygons##2014-03-30 04:00:00##409
466##Distinct Terms in a Multiplication Table##2014-04-06 06:00:00##515
467##Superinteger##2014-04-13 09:00:00##669
468##Smooth Divisors of Binomial Coefficients##2014-04-19 12:00:00##457
469##Empty Chairs##2014-04-26 15:00:00##1046
470##Super Ramvok##2014-05-03 18:00:00##393
471##Triangle Inscribed in Ellipse##2014-05-10 21:00:00##399
472##Comfortable Distance II##2014-05-18 00:00:00##402
473##Phigital Number Base##2014-05-25 03:00:00##1012
474##Last Digits of Divisors##2014-06-01 06:00:00##624
475##Music Festival##2014-06-08 09:00:00##684
476##Circle Packing II##2014-06-14 12:00:00##575
477##Number Sequence Game##2014-08-23 15:00:00##404
478##Mixtures##2014-08-30 18:00:00##434
479##Roots on the Rise##2014-09-06 21:00:00##1730
480##The Last Question##2014-09-14 00:00:00##843
481##Chef Showdown##2014-09-21 03:00:00##409
482##The Incenter of a Triangle##2014-09-28 06:00:00##371
483##Repeated Permutation##2014-10-05 09:00:00##485
484##Arithmetic Derivative##2014-10-11 12:00:00##667
485##Maximum Number of Divisors##2014-10-18 15:00:00##1568
486##Palindrome-containing Strings##2014-10-25 18:00:00##427
487##Sums of Power Sums##2014-11-01 22:00:00##940
488##Unbalanced Nim##2014-11-09 01:00:00##371
489##Common Factors Between Two Sequences##2014-11-16 04:00:00##430
490##Jumping Frog##2014-11-23 07:00:00##498
491##Double Pandigital Number Divisible by $11$##2014-11-30 10:00:00##2742
492##Exploding Sequence##2014-12-06 13:00:00##529
493##Under the Rainbow##2014-12-13 16:00:00##6678
494##Collatz Prefix Families##2014-12-20 19:00:00##416
495##Writing $n$ as the Product of $k$ Distinct Positive Integers##2014-12-27 22:00:00##585
496##Incenter and Circumcenter of Triangle##2015-01-04 01:00:00##502
497##Drunken Tower of Hanoi##2015-01-11 04:00:00##811
498##Remainder of Polynomial Division##2015-01-18 07:00:00##747
499##St. Petersburg Lottery##2015-01-25 10:00:00##611
500##Problem 500!!!##2015-01-31 13:00:00##5161
501##Eight Divisors##2015-01-31 13:00:00##1810
502##Counting Castles##2015-02-07 16:00:00##510
503##Compromise or Persist##2015-02-14 19:00:00##494
504##Square on the Inside##2015-02-21 22:00:00##3925
505##Bidirectional Recurrence##2015-03-01 01:00:00##349
506##Clock Sequence##2015-03-08 04:00:00##1236
507##Shortest Lattice Vector##2015-03-15 07:00:00##348
508##Integers in Base $i-1$##2015-03-22 10:00:00##377
509##Divisor Nim##2015-03-28 13:00:00##863
510##Tangent Circles##2015-04-04 15:00:00##1393
511##Sequences with Nice Divisibility Properties##2015-04-11 18:00:00##620
512##Sums of Totients of Powers##2015-04-18 21:00:00##1981
513##Integral Median##2015-04-26 00:00:00##458
514##Geoboard Shapes##2015-05-03 03:00:00##370
515##Dissonant Numbers##2015-05-10 06:00:00##672
516##$5$-smooth Totients##2015-05-17 09:00:00##2030
517##A Real Recursion##2015-05-23 12:00:00##658
518##Prime Triples and Geometric Sequences##2015-05-30 15:00:00##2150
519##Tricoloured Coin Fountains##2015-06-06 18:00:00##520
520##Simbers##2015-06-13 21:00:00##640
521##Smallest Prime Factor##2015-06-21 00:00:00##1058
522##Hilbert's Blackout##2015-06-28 03:00:00##414
523##First Sort I##2015-09-06 06:00:00##1380
524##First Sort II##2015-09-06 06:00:00##345
525##Rolling Ellipse##2015-09-13 09:00:00##717
526##Largest Prime Factors of Consecutive Numbers##2015-09-19 12:00:00##472
527##Randomized Binary Search##2015-09-26 15:00:00##1030
528##Constrained Sums##2015-10-03 18:00:00##468
529##$10$-substrings##2015-10-10 21:00:00##427
530##GCD of Divisors##2015-10-18 00:00:00##655
531##Chinese Leftovers##2015-10-25 04:00:00##1590
532##Nanobots on Geodesics##2015-11-01 07:00:00##447
533##Minimum Values of the Carmichael Function##2015-11-08 10:00:00##484
534##Weak Queens##2015-11-14 13:00:00##473
535##Fractal Sequence##2015-11-21 16:00:00##417
536##Modulo Power Identity ##2015-11-28 19:00:00##434
537##Counting Tuples##2015-12-05 22:00:00##928
538##Maximum Quadrilaterals##2015-12-13 01:00:00##474
539##Odd Elimination##2015-12-20 04:00:00##1133
540##Counting Primitive Pythagorean Triples##2015-12-27 07:00:00##939
541##Divisibility of Harmonic Number Denominators##2016-01-03 10:00:00##360
542##Geometric Progression with Maximum Sum##2016-01-09 13:00:00##352
543##Prime-Sum Numbers##2016-01-16 16:00:00##1040
544##Chromatic Conundrum##2016-01-23 19:00:00##403
545##Faulhaber's Formulas##2016-01-30 22:00:00##780
546##The Floor's Revenge##2016-02-07 01:00:00##382
547##Distance of Random Points Within Hollow Square Laminae##2016-02-14 04:00:00##347
548##Gozinta Chains##2016-02-21 07:00:00##861
549##Divisibility of Factorials##2016-02-28 10:00:00##3626
550##Divisor Game##2016-03-05 13:00:00##510
551##Sum of Digits Sequence##2016-03-12 16:00:00##664
552##Chinese Leftovers II##2016-03-19 19:00:00##633
553##Power Sets of Power Sets##2016-03-26 22:00:00##356
554##Centaurs on a Chess Board##2016-04-03 00:00:00##388
555##McCarthy 91 Function##2016-04-10 03:00:00##977
556##Squarefree Gaussian Integers##2016-04-17 06:00:00##400
557##Cutting Triangles##2016-04-24 09:00:00##414
558##Irrational Base##2016-04-30 12:00:00##365
559##Permuted Matrices##2016-05-07 15:00:00##360
560##Coprime Nim##2016-05-14 18:00:00##493
561##Divisor Pairs##2016-05-21 21:00:00##1104
562##Maximal Perimeter##2016-05-29 00:00:00##301
563##Robot Welders##2016-06-05 03:00:00##493
564##Maximal Polygons##2016-06-12 06:00:00##360
565##Divisibility of Sum of Divisors##2016-06-19 09:00:00##850
566##Cake Icing Puzzle##2016-06-25 12:00:00##451
567##Reciprocal Games I##2016-09-03 15:00:00##439
568##Reciprocal Games II##2016-09-03 15:00:00##421
569##Prime Mountain Range##2016-09-10 18:00:00##556
570##Snowflakes##2016-09-17 21:00:00##392
571##Super Pandigital Numbers##2016-09-25 00:00:00##1483
572##Idempotent Matrices##2016-10-02 03:00:00##495
573##Unfair Race##2016-10-09 06:00:00##340
574##Verifying Primes##2016-10-16 09:00:00##387
575##Wandering Robots##2016-10-22 12:00:00##801
576##Irrational Jumps##2016-10-29 15:00:00##334
577##Counting Hexagons##2016-11-12 19:00:00##2039
578##Integers with Decreasing Prime Powers##2016-11-19 22:00:00##379
579##Lattice Points in Lattice Cubes##2016-11-27 01:00:00##385
580##Squarefree Hilbert Numbers##2016-12-04 04:00:00##393
581##$47$-smooth Triangular Numbers##2016-12-11 07:00:00##1181
582##Nearly Isosceles $120$ Degree Triangles##2016-12-18 10:00:00##476
583##Heron Envelopes##2016-12-24 13:00:00##522
584##Birthday Problem Revisited##2016-12-31 16:00:00##408
585##Nested Square Roots##2017-01-07 19:00:00##406
586##Binary Quadratic Form##2017-01-14 22:00:00##360
587##Concave Triangle##2017-01-22 01:00:00##4187
588##Quintinomial Coefficients##2017-01-29 04:00:00##614
589##Poohsticks Marathon##2017-02-05 07:00:00##332
590##Sets with a Given Least Common Multiple##2017-02-12 10:00:00##391
591##Best Approximations by Quadratic Integers##2017-02-18 13:00:00##344
592##Factorial Trailing Digits 2##2017-02-25 16:00:00##436
593##Fleeting Medians##2017-03-04 19:00:00##769
594##Rhombus Tilings##2017-03-11 22:00:00##306
595##Incremental Random Sort##2017-03-19 01:00:00##881
596##Number of Lattice Points in a Hyperball##2017-03-26 03:00:00##529
597##Torpids##2017-04-02 06:00:00##468
598##Split Divisibilities##2017-04-09 09:00:00##682
599##Distinct Colourings of a Rubik's Cube##2017-04-15 12:00:00##459
600##Integer Sided Equiangular Hexagons##2017-04-22 15:00:00##842
601##Divisibility Streaks##2017-04-29 18:00:00##2726
602##Product of Head Counts##2017-05-06 21:00:00##708
603##Substring Sums of Prime Concatenations##2017-05-14 00:00:00##588
604##Convex Path in Square##2017-05-21 03:00:00##709
605##Pairwise Coin-Tossing Game##2017-05-28 06:00:00##1142
606##Gozinta Chains II##2017-06-04 09:00:00##530
607##Marsh Crossing##2017-06-10 12:00:00##2191
608##Divisor Sums##2017-06-17 15:00:00##469
609##$\pi$ Sequences##2017-09-09 15:00:00##1221
610##Roman Numerals II##2017-09-23 18:00:00##853
611##Hallway of Square Steps##2017-10-07 21:00:00##460
612##Friend Numbers##2017-10-22 00:00:00##964
613##Pythagorean Ant##2017-11-05 04:00:00##2314
614##Special Partitions 2##2017-11-19 07:00:00##449
615##The Millionth Number with at Least One Million Prime Factors##2017-12-03 10:00:00##816
616##Creative Numbers##2017-12-16 13:00:00##648
617##Mirror Power Sequence##2017-12-30 16:00:00##509
618##Numbers with a Given Prime Factor Sum##2018-01-13 19:00:00##1389
619##Square Subsets##2018-01-27 22:00:00##595
620##Planetary Gears##2018-02-11 01:00:00##272
621##Expressing an Integer as the Sum of Triangular Numbers##2018-02-25 04:00:00##769
622##Riffle Shuffles##2018-03-11 07:00:00##2195
623##Lambda Count##2018-03-25 09:00:00##468
624##Two Heads Are Better Than One##2018-04-07 12:00:00##873
625##Gcd Sum##2018-04-21 15:00:00##959
626##Counting Binary Matrices##2018-05-05 18:00:00##374
627##Counting Products##2018-05-19 21:00:00##366
628##Open Chess Positions##2018-06-03 00:00:00##1090
629##Scatterstone Nim##2018-06-17 03:00:00##354
630##Crossed Lines##2018-07-01 06:00:00##1382
631##Constrained Permutations##2018-07-15 09:00:00##282
632##Square Prime Factors##2018-07-28 12:00:00##700
633##Square Prime Factors II##2018-07-28 12:00:00##465
634##Numbers of the Form $a^2b^3$##2018-08-11 15:00:00##855
635##Subset Sums##2018-08-25 18:00:00##541
636##Restricted Factorisations##2018-09-08 21:00:00##337
637##Flexible Digit Sum##2018-09-23 00:00:00##470
638##Weighted Lattice Paths##2018-10-07 03:00:00##534
639##Summing a Multiplicative Function##2018-10-21 06:00:00##425
640##Shut the Box##2018-10-28 10:00:00##512
641##A Long Row of Dice##2018-11-03 13:00:00##688
642##Sum of Largest Prime Factors##2018-11-10 16:00:00##528
643##$2$-Friendly##2018-11-17 19:00:00##911
644##Squares on the Line##2018-11-24 22:00:00##282
645##Every Day Is a Holiday##2018-12-02 01:00:00##350
646##Bounded Divisors##2018-12-09 04:00:00##421
647##Linear Transformations of Polygonal Numbers##2018-12-16 07:00:00##615
648##Skipping Squares##2018-12-23 10:00:00##420
649##Low-Prime Chessboard Nim##2018-12-29 13:00:00##611
650##Divisors of Binomial Product##2019-01-05 16:00:00##2272
651##Patterned Cylinders##2019-01-12 19:00:00##281
652##Distinct Values of a Proto-logarithmic Function##2019-01-19 22:00:00##256
653##Frictionless Tube##2019-01-27 01:00:00##449
654##Neighbourly Constraints##2019-02-03 04:00:00##493
655##Divisible Palindromes##2019-02-10 07:00:00##787
656##Palindromic Sequences##2019-02-17 10:00:00##346
657##Incomplete Words##2019-02-23 13:00:00##798
658##Incomplete Words II##2019-02-23 13:00:00##347
659##Largest Prime##2019-03-02 16:00:00##1335
660##Pandigital Triangles##2019-03-09 19:00:00##441
661##A Long Chess Match##2019-03-16 22:00:00##345
662##Fibonacci Paths##2019-03-24 01:00:00##1123
663##Sums of Subarrays##2019-03-31 03:00:00##508
664##An Infinite Game##2019-04-07 06:00:00##297
665##Proportionate Nim##2019-04-14 09:00:00##358
666##Polymorphic Bacteria##2019-04-20 12:00:00##449
667##Moving Pentagon##2019-04-27 15:00:00##326
668##Square Root Smooth Numbers##2019-05-04 18:00:00##1383
669##The King's Banquet##2019-05-11 21:00:00##444
670##Colouring a Strip##2019-05-19 00:00:00##509
671##Colouring a Loop##2019-05-19 00:00:00##276
672##One More One##2019-05-26 03:00:00##391
673##Beds and Desks##2019-06-02 06:00:00##478
674##Solving $\mathcal{I}$-equations##2019-06-09 09:00:00##270
675##$2^{\omega(n)}$##2019-06-15 12:00:00##1084
676##Matching Digit Sums##2019-06-22 15:00:00##334
677##Coloured Graphs##2019-06-29 18:00:00##320
678##Fermat-like Equations##2019-09-07 21:00:00##359
679##Freefarea##2019-09-15 00:00:00##1305
680##Yarra Gnisrever##2019-09-22 03:00:00##304
681##Maximal Area##2019-09-29 06:00:00##334
682##$5$-Smooth Pairs##2019-10-06 09:00:00##391
683##The Chase II##2019-10-12 12:00:00##450
684##Inverse Digit Sum##2019-10-19 15:00:00##3537
685##Inverse Digit Sum II##2019-10-19 15:00:00##294
686##Powers of Two##2019-10-26 18:00:00##4842
687##Shuffling Cards##2019-11-02 22:00:00##444
688##Piles of Plates##2019-11-10 01:00:00##1050
689##Binary Series##2019-11-17 04:00:00##369
690##Tom and Jerry##2019-11-24 07:00:00##318
691##Long Substring with Many Repetitions##2019-12-01 10:00:00##394
692##Siegbert and Jo##2019-12-07 13:00:00##1930
693##Finite Sequence Generator##2019-12-14 16:00:00##388
694##Cube-full Divisors##2019-12-21 19:00:00##1405
695##Random Rectangles##2019-12-28 22:00:00##336
696##Mahjong##2020-01-05 01:00:00##369
697##Randomly Decaying Sequence##2020-01-12 04:00:00##817
698##123 Numbers##2020-01-19 07:00:00##649
699##Triffle Numbers##2020-01-26 10:00:00##286
700##Eulercoin##2020-02-01 13:00:00##4723
701##Random Connected Area##2020-02-08 16:00:00##537
702##Jumping Flea##2020-02-15 19:00:00##290
703##Circular Logic II##2020-02-22 22:00:00##471
704##Factors of Two in Binomial Coefficients##2020-03-01 01:00:00##1411
705##Total Inversion Count of Divided Sequences##2020-03-08 04:00:00##663
706##$3$-Like Numbers##2020-03-15 07:00:00##842
707##Lights Out##2020-03-22 10:00:00##359
708##Twos Are All You Need##2020-03-28 13:00:00##501
709##Even Stevens##2020-04-04 16:00:00##1241
710##One Million Members##2020-04-11 19:00:00##1803
711##Binary Blackboard##2020-04-11 19:00:00##498
712##Exponent Difference##2020-04-18 22:00:00##702
713##Turán's Water Heating System##2020-04-26 01:00:00##1015
714##Duodigits##2020-05-03 04:00:00##993
715##Sextuplet Norms##2020-05-10 07:00:00##303
716##Grid Graphs##2020-05-17 10:00:00##349
717##Summation of a Modular Formula##2020-05-23 13:00:00##740
718##Unreachable Numbers##2020-05-30 16:00:00##490
719##Number Splitting##2020-06-06 19:00:00##5693
720##Unpredictable Permutations##2020-06-13 22:00:00##437
721##High Powers of Irrational Numbers##2020-06-21 01:00:00##623
722##Slowly Converging Series##2020-06-28 04:00:00##723
723##Pythagorean Quadrilaterals##2020-07-05 07:00:00##282
724##Drone Delivery##2020-09-05 13:00:00##596
725##Digit Sum Numbers##2020-09-12 16:00:00##1576
726##Falling Bottles##2020-09-19 19:00:00##295
727##Triangle of Circular Arcs##2020-09-26 22:00:00##733
728##Circle of Coins##2020-10-04 01:00:00##423
729##Range of Periodic Sequence##2020-10-11 04:00:00##372
730##Shifted Pythagorean Triples##2020-10-18 07:00:00##272
731##A Stoneham Number##2020-10-25 10:00:00##813
732##Standing on the Shoulders of Trolls##2020-10-31 13:00:00##330
733##Ascending Subsequences##2020-11-07 16:00:00##675
734##A Bit of Prime##2020-11-14 19:00:00##509
735##Divisors of $2n^2$##2020-11-21 22:00:00##347
736##Paths to Equality##2020-11-29 01:00:00##335
737##Coin Loops##2020-12-06 04:00:00##540
738##Counting Ordered Factorisations##2020-12-13 07:00:00##409
739##Summation of Summations##2020-12-20 10:00:00##761
740##Secret Santa##2020-12-26 13:00:00##302
741##Binary Grid Colouring##2021-01-02 16:00:00##262
742##Minimum Area of a Convex Grid Polygon##2021-01-09 19:00:00##254
743##Window into a Matrix##2021-01-16 22:00:00##1712
744##What? Where? When?##2021-01-24 01:00:00##449
745##Sum of Squares II##2021-01-31 04:00:00##1789
746##A Messy Dinner##2021-02-07 07:00:00##424
747##Triangular Pizza##2021-02-14 10:00:00##302
748##Upside Down Diophantine Equation##2021-02-20 13:00:00##439
749##Near Power Sums##2021-02-27 16:00:00##1029
750##Optimal Card Stacking##2021-03-06 19:00:00##470
751##Concatenation Coincidence##2021-03-13 22:00:00##3254
752##Powers of $1+\sqrt 7$##2021-03-21 01:00:00##946
753##Fermat Equation##2021-03-28 04:00:00##589
754##Product of Gauss Factorials##2021-04-04 07:00:00##987
755##Not Zeckendorf##2021-04-18 10:00:00##1287
756##Approximating a Sum##2021-05-01 13:00:00##479
757##Stealthy Numbers##2021-05-15 16:00:00##1827
758##Buckets of Water##2021-05-29 19:00:00##333
759##A Squared Recurrence Relation##2021-06-12 22:00:00##804
760##Sum over Bitwise Operators##2021-06-27 01:00:00##622
761##Runner and Swimmer##2021-07-11 04:00:00##307
762##Amoebas in a 2D Grid##2021-09-04 13:00:00##342
763##Amoebas in a 3D Grid##2021-09-04 13:00:00##377
764##Asymmetric Diophantine Equation##2021-09-11 16:00:00##560
765##Trillionaire##2021-09-18 19:00:00##329
766##Sliding Block Puzzle##2021-10-02 22:00:00##480
767##Window into a Matrix II##2021-10-10 01:00:00##271
768##Chandelier##2021-10-17 04:00:00##315
769##Binary Quadratic Form II##2021-10-24 06:00:00##249
770##Delphi Flip##2021-10-31 10:00:00##748
771##Pseudo Geometric Sequences##2021-11-06 13:00:00##205
772##Balanceable $k$-bounded Partitions##2021-11-13 16:00:00##784
773##Ruff Numbers##2021-11-20 19:00:00##305
774##Conjunctive Sequences##2021-11-27 22:00:00##237
775##Saving Paper##2021-12-05 01:00:00##359
776##Digit Sum Division##2021-12-12 04:00:00##777
777##Lissajous Curves##2021-12-19 07:00:00##223
778##Freshman's Product##2021-12-26 10:00:00##610
779##Prime Factor and Exponent##2022-01-01 13:00:00##711
780##Toriangulations##2022-01-08 16:00:00##302
781##Feynman Diagrams##2022-01-15 19:00:00##231
782##Distinct Rows and Columns##2022-01-22 22:00:00##247
783##Urns##2022-01-30 01:00:00##281
784##Reciprocal Pairs##2022-02-06 04:00:00##593
785##Symmetric Diophantine Equation##2022-02-13 07:00:00##303
786##Billiard##2022-02-20 10:00:00##249
787##Bézout's Game##2022-02-26 13:00:00##297
788##Dominating Numbers##2022-03-05 16:00:00##1822
789##Minimal Pairing Modulo $p$##2022-03-12 19:00:00##310
790##Clock Grid##2022-03-19 22:00:00##386
791##Average and Variance##2022-03-27 01:00:00##258
792##Too Many Twos##2022-04-03 04:00:00##300
793##Median of Products##2022-04-10 07:00:00##965
794##Seventeen Points##2022-04-17 10:00:00##469
795##Alternating GCD Sum##2022-04-23 13:00:00##544
796##A Grand Shuffle##2022-04-30 16:00:00##313
797##Cyclogenic Polynomials##2022-05-07 19:00:00##299
798##Card Stacking Game##2022-05-14 22:00:00##255
799##Pentagonal Puzzle##2022-05-22 01:00:00##340
800##Hybrid Integers##2022-05-29 04:00:00##2860
801##$x^y \equiv y^x$##2022-06-05 07:00:00##456
802##Iterated Composition##2022-06-12 10:00:00##396
803##Pseudorandom Sequence##2022-06-18 13:00:00##331
804##Counting Binary Quadratic Representations##2022-06-25 16:00:00##968
805##Shifted Multiples##2022-07-02 19:00:00##271
806##Nim on Towers of Hanoi##2022-07-09 22:00:00##249
807##Loops of Ropes##2022-09-11 01:00:00##221
808##Reversible Prime Squares##2022-09-18 04:00:00##4286
809##Rational Recurrence Relation ##2022-09-25 07:00:00##431
810##XOR-Primes##2022-10-02 10:00:00##1018
811##Bitwise Recursion##2022-10-08 13:00:00##347
812##Dynamical Polynomials##2022-10-15 16:00:00##275
813##XOR-Powers##2022-10-22 19:00:00##814
814##Mezzo-forte##2022-10-29 22:00:00##330
815##Group by Value##2022-11-06 01:00:00##603
816##Shortest Distance Among Points##2022-11-13 04:00:00##3174
817##Digits in Squares##2022-11-20 07:00:00##646
818##SET##2022-11-27 10:00:00##236
819##Iterative Sampling##2022-12-03 13:00:00##339
820##$N$<sup>th</sup> Digit of Reciprocals##2022-12-10 16:00:00##1621
821##123-Separable##2022-12-17 19:00:00##247
822##Square the Smallest##2022-12-24 22:00:00##1175
823##Factor Shuffle##2023-01-01 01:00:00##284
824##Chess Sliders##2023-01-08 04:00:00##246
825##Chasing Game##2023-01-15 07:00:00##238
826##Birds on a Wire##2023-01-22 10:00:00##385
827##Pythagorean Triple Occurrence##2023-01-28 13:00:00##268
828##Numbers Challenge##2023-02-04 16:00:00##927
829##Integral Fusion##2023-02-11 19:00:00##305
830##Binomials and Powers##2023-02-18 22:00:00##262
831##Triple Product##2023-02-26 01:00:00##294
832##Mex Sequence##2023-03-05 04:00:00##473
833##Square Triangle Products##2023-03-12 07:00:00##251
834##Add and Divide##2023-03-19 10:00:00##603
835##Supernatural Triangles##2023-03-25 13:00:00##554
836##A Bold Proposition##2023-04-01 16:00:00##7268
837##Amidakuji##2023-04-01 16:00:00##311
838##Not Coprime##2023-04-08 19:00:00##815
839##Beans in Bowls##2023-04-15 22:00:00##514
840##Sum of Products##2023-04-23 01:00:00##553
841##Regular Star Polygons##2023-04-30 04:00:00##265
842##Irregular Star Polygons##2023-05-07 07:00:00##198
843##Periodic Circles##2023-05-14 10:00:00##208
844##$k$-Markov Numbers##2023-05-20 13:00:00##305
845##Prime Digit Sum##2023-05-27 16:00:00##1257
846##Magic Bracelets##2023-06-03 19:00:00##302
847##Jack's Bean##2023-06-10 22:00:00##189
848##Guessing with Sets##2023-06-18 01:00:00##294
849##The Tournament##2023-06-25 04:00:00##370
850##Fractions of Powers##2023-07-02 07:00:00##214
851##SOP and POS##2023-07-09 10:00:00##256
852##Coins in a Box##2023-09-02 13:00:00##338
853##Pisano Periods 1##2023-09-09 16:00:00##1967
854##Pisano Periods 2##2023-09-09 16:00:00##498
855##Delphi Paper##2023-09-16 19:00:00##214
856##Waiting for a Pair##2023-09-23 22:00:00##876
857##Beautiful Graphs##2023-10-01 01:00:00##262
858##LCM##2023-10-08 04:00:00##344
859##Cookie Game##2023-10-15 07:00:00##323
860##Gold and Silver Coin Game##2023-10-22 10:00:00##692
861##Products of Bi-Unitary Divisors##2023-10-28 13:00:00##301
862##Larger Digit Permutation##2023-11-04 16:00:00##1146
863##Different Dice##2023-11-11 19:00:00##335
864##Square + 1 = Squarefree##2023-11-18 22:00:00##279
865##Triplicate Numbers##2023-11-26 01:00:00##393
866##Tidying Up B##2023-12-03 04:00:00##631
867##Tiling Dodecagon##2023-12-10 07:00:00##242
868##Belfry Maths##2023-12-17 10:00:00##675
869##Prime Guessing##2023-12-23 13:00:00##1034
870##Stone Game IV##2023-12-30 16:00:00##219
871##Drifting Subsets##2024-01-06 19:00:00##478
872##Recursive Tree##2024-01-13 22:00:00##1558
873##Words with Gaps##2024-01-21 01:00:00##468
874##Maximal Prime Score##2024-01-28 04:00:00##706
875##Quadruple Congruence##2024-02-04 07:00:00##312
876##Triplet Tricks##2024-02-11 10:00:00##191
877##XOR-Equation A##2024-02-17 13:00:00##628
878##XOR-Equation B##2024-02-17 13:00:00##370
879##Touch-screen Password##2024-02-24 16:00:00##609
880##Nested Radicals##2024-03-02 19:00:00##180
881##Divisor Graph Width##2024-03-09 22:00:00##690
882##Removing Bits##2024-03-17 01:00:00##293
883##Remarkable Triangles##2024-03-24 04:00:00##178
884##Removing Cubes##2024-03-31 07:00:00##800
885##Sorted Digits##2024-04-07 10:00:00##1400
886##Coprime Permutations##2024-04-13 13:00:00##387
887##Bounded Binary Search##2024-04-20 16:00:00##381
888##1249 Nim##2024-04-27 19:00:00##274
889##Rational Blancmange##2024-05-04 22:00:00##189
890##Binary Partitions##2024-05-12 01:00:00##318
891##Ambiguous Clock##2024-05-19 04:00:00##237
892##Zebra Circles##2024-05-26 07:00:00##220
893##Matchsticks##2024-06-02 10:00:00##823
894##Spiral of Circles##2024-06-08 13:00:00##449
895##Gold &amp; Silver Coin Game II##2024-06-15 16:00:00##186
896##Divisible Ranges##2024-06-22 19:00:00##297
897##Maximal $n$-gon in a region##2024-06-29 22:00:00##559
898##Claire Voyant##2024-07-07 01:00:00##427
899##DistribuNim I##2024-07-14 04:00:00##754
900##DistribuNim II##2024-07-14 04:00:00##224
901##Well Drilling##2024-07-21 07:00:00##680
902##Permutation Powers##2024-07-28 10:00:00##261
903##Total Permutation Powers##2024-07-28 10:00:00##228
904##Pythagorean Angle##2024-08-24 13:00:00##311
905##Now I Know##2024-08-31 16:00:00##459
906##A Collective Decision##2024-09-07 19:00:00##333
907##Stacking Cups##2024-09-14 22:00:00##393
908##Clock Sequence II##2024-09-22 01:00:00##220
909##L-expressions I##2024-09-29 04:00:00##284
910##L-expressions II##2024-09-29 04:00:00##187
911##Khinchin Exceptions##2024-10-06 07:00:00##264
912##Where are the Odds?##2024-10-13 10:00:00##285
913##Row-major vs Column-major##2024-10-19 13:00:00##230
914##Triangles inside Circles##2024-10-26 16:00:00##694
915##Giant GCDs##2024-11-02 19:00:00##312
916##Restricted Permutations##2024-11-09 22:00:00##250
917##Minimal Path Using Additive Cost##2024-11-17 01:00:00##308
918##Recursive Sequence Summation##2024-11-24 04:00:00##1704
919##Fortunate Triangles##2024-12-01 07:00:00##352
920##Tau Numbers##2024-12-08 10:00:00##394
921##Golden Recurrence##2024-12-14 13:00:00##298
922##Young's Game A##2024-12-21 16:00:00##196
923##Young's Game B##2024-12-21 16:00:00##168
924##Larger Digit Permutation II##2024-12-28 19:00:00##281
925##Larger Digit Permutation III##2024-12-28 19:00:00##234
926##Total Roundness##2025-01-04 22:00:00##938
927##Prime-ary Tree##2025-01-12 01:00:00##247
928##Cribbage##2025-01-19 04:00:00##319
929##Odd-Run Compositions##2025-01-26 07:00:00##322
930##The Gathering##2025-02-02 10:00:00##200
931##Totient Graph##2025-02-08 13:00:00##225
932##$2025$##2025-02-15 16:00:00##2360
933##Paper Cutting##2025-02-22 19:00:00##222
934##Unlucky Primes##2025-03-01 22:00:00##552
935##Rolling Square##2025-03-09 01:00:00##176
936##Peerless Trees##2025-03-16 04:00:00##186
937##Equiproduct Partition##2025-03-23 07:00:00##222
938##Exhausting a Colour##2025-03-30 10:00:00##1476
939##Partisan Nim##2025-04-05 13:00:00##194
940##Two-Dimensional Recurrence##2025-04-12 16:00:00##776
941##de Bruijn's Combination Lock##2025-04-19 19:00:00##181
942##Mersenne's Square Root##2025-04-26 22:00:00##222
943##Self Describing Sequences##2025-05-04 01:00:00##165
944##Sum of Elevisors##2025-05-11 04:00:00##1012
945##XOR-Equation C##2025-05-18 07:00:00##277
946##Continued Fraction Fraction##2025-05-25 10:00:00##364
947##Fibonacci Residues##2025-05-31 13:00:00##225
948##Left vs Right##2025-06-07 16:00:00##488
949##Left vs Right II##2025-06-07 16:00:00##225
950##Pirate Treasure##2025-06-14 19:00:00##185
951##A Game of Chance##2025-06-21 22:00:00##531
952##Order Modulo Factorial##2025-06-29 01:00:00##391
953##Factorisation Nim##2025-07-06 04:00:00##288
954##Heptaphobia##2025-07-13 07:00:00##262
955##Finding Triangles##2025-07-20 10:00:00##797
956##Super Duper Sum##2025-07-26 13:00:00##612
957##Point Genesis##2025-08-02 16:00:00##233
958##Euclid's Labour##2025-08-30 19:00:00##281
959##Asymmetric Random Walk##2025-09-06 22:00:00##353
960##Stone Game Solitaire##2025-09-14 01:00:00##252
961##Removing Digits##2025-09-21 04:00:00##1139
962##Angular Bisector and Tangent 2##2025-09-28 07:00:00##177
963##Removing Trits##2025-10-05 10:00:00##181
964##Musical Chairs Revisited##2025-10-11 13:00:00##245
965##Expected Minimal Fractional Value##2025-10-18 16:00:00##695
966##Triangle Circle Intersection##2025-10-25 19:00:00##208
967##$B$-Trivisible Numbers##2025-11-01 22:00:00##306
968##5D Summation##2025-11-09 01:00:00##184
969##Kangaroo Hopping##2025-11-16 04:00:00##365
970##Kangaroo Hopping over Sixes##2025-11-16 04:00:00##234
971##Modular Polynomial Composition##2025-11-23 07:00:00##274
972##Hyperbolic Plane##2025-11-30 10:00:00##286
973##Random Dealings##2025-12-06 13:00:00##181
974##Very Odd Numbers##2025-12-13 16:00:00##605
975##A Winding Path##2025-12-20 19:00:00##188
976##XO Game##2025-12-27 22:00:00##168
977##Iterated Functions##2026-01-04 01:00:00##231
978##Random Walk Skewness##2026-01-11 04:00:00##516
979##Heptagon Hopping##2026-01-18 07:00:00##296
980##The Quaternion Group I##2026-01-25 10:00:00##480
981##The Quaternion Group II##2026-01-25 10:00:00##308
982##The Third Dice##2026-01-31 13:00:00##229
983##Consonant Circle Crossing##2026-02-07 16:00:00##186
984##Knights and Horses##2026-02-14 19:00:00##169
985##Telescoping Triangles##2026-02-21 22:00:00##466
986##Another Infinite Game##2026-03-01 01:00:00##169
987##Straight Eight##2026-03-08 04:00:00##231
988##Non-attacking Frogs##2026-03-15 07:00:00##258
989##Fibonacci Sum##2026-03-22 10:00:00##168
990##Addition Equations##2026-03-28 13:00:00##186
991##Fruit Salad##2026-04-04 16:00:00##491
992##Another Frog Jumping##2026-04-11 19:00:00##241
993##Banana Beaver##2026-04-18 22:00:00##228
994##Counting Triangles##2026-04-26 01:00:00##176
995##A Particular Pair of Polynomials##2026-05-03 04:00:00##167
996##Overtakes##2026-05-10 07:00:00##167
997##Dice Box##2026-05-17 10:00:00##336
998##Squaring the Triangle##2026-05-23 13:00:00##139
999##Alternating Recurrence##2026-05-30 16:00:00##164
1000##Problem $1000$##2026-06-06 19:00:00##426
1001##Connections I##2026-06-13 22:00:00##184
1002##Connections II##2026-06-13 22:00:00##166
1003##Lonely Singles##2026-06-21 01:00:00##160
1004##Balanced Integer##2026-06-28 04:00:00##145
1005##Median Prime List##2026-07-05 07:00:00##459
1006##Fibonacci Subwords##2026-07-12 10:00:00##65
1007##Alternating Difference##2026-07-12 10:00:00##122