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Problems Archives

The problems archives table shows problems 1 to 666. 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
1499
602Product of Head Counts
354
603Substring sums of prime concatenations
306
604Convex path in square
396
605Pairwise Coin-Tossing Game
612
606Gozinta Chains II
294
607Marsh Crossing
1245
608Divisor Sums
233
609π sequences
632
610Roman Numerals II
429
611Hallway of square steps
252
612Friend numbers
476
613Pythagorean Ant
1264
614Special partitions 2
235
615The millionth number with at least one million prime factors
439
616Creative numbers
375
617Mirror Power Sequence
304
618Numbers with a given prime factor sum
702
619Square subsets
303
620Planetary Gears
151
621Expressing an integer as the sum of triangular numbers
420
622Riffle Shuffles
1125
623Lambda Count
247
624Two heads are better than one
435
625Gcd sum
381
626Counting Binary Matrices
169
627Counting products
193
628Open chess positions
548
629Scatterstone Nim
180
630Crossed lines
671
631Constrained Permutations
158
632Square prime factors
323
633Square prime factors II
243
634Numbers of the form $a^2b^3$
405
635Subset sums
229
636Restricted Factorisations
112
637Flexible digit sum
238
638Weighted lattice paths
252
639Summing a multiplicative function
149
640Shut the Box
244
641A Long Row of Dice
297
642Sum of largest prime factors
242
6432-Friendly
340
644Squares on the line
114
645Every Day is a Holiday
137
646Bounded Divisors
196
647Linear Transformations of Polygonal Numbers
286
648Skipping Squares
207
649Low-Prime Chessboard Nim
246
650Divisors of Binomial Product
670