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Problems Archives

The problems archives table shows problems 1 to 646. If you would like to tackle the 10 most recently published problems then go to Recent problems.
Click the description/title of the problem to view details and submit your answer.


IDDescription / TitleSolved By
601Divisibility streaks
1402
602Product of Head Counts
347
603Substring sums of prime concatenations
290
604Convex path in square
384
605Pairwise Coin-Tossing Game
580
606Gozinta Chains II
283
607Marsh Crossing
1172
608Divisor Sums
223
609π sequences
586
610Roman Numerals II
412
611Hallway of square steps
248
612Friend numbers
457
613Pythagorean Ant
1171
614Special partitions 2
229
615The millionth number with at least one million prime factors
423
616Creative numbers
364
617Mirror Power Sequence
292
618Numbers with a given prime factor sum
647
619Square subsets
292
620Planetary Gears
148
621Expressing an integer as the sum of triangular numbers
402
622Riffle Shuffles
1008
623Lambda Count
239
624Two heads are better than one
404
625Gcd sum
353
626Counting Binary Matrices
163
627Counting products
187
628Open chess positions
494
629Scatterstone Nim
170
630Crossed lines
581
631Constrained Permutations
152
632Square prime factors
302
633Square prime factors II
229
634Numbers of the form $a^2b^3$
379
635Subset sums
214
636Restricted Factorisations
104
637Flexible digit sum
227
638Weighted lattice paths
230
639Summing a multiplicative function
134
640Shut the Box
222
641A Long Row of Dice
267
642Sum of largest prime factors
213
6432-Friendly
278
644Squares on the line
83
645Every Day is a Holiday
120
646Bounded Divisors
167