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Problems Archives

The problems archives table shows problems 1 to 745. 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.


ID

Description / TitleSolved By
601Divisibility streaks
1839
602Product of Head Counts
439
603Substring sums of prime concatenations
373
604Convex path in square
458
605Pairwise Coin-Tossing Game
748
606Gozinta Chains II
341
607Marsh Crossing
1544
608Divisor Sums
274
609π sequences
839
610Roman Numerals II
519
611Hallway of square steps
295
612Friend numbers
589
613Pythagorean Ant
1608
614Special partitions 2
275
615The millionth number with at least one million prime factors
524
616Creative numbers
445
617Mirror Power Sequence
352
618Numbers with a given prime factor sum
905
619Square subsets
359
620Planetary Gears
161
621Expressing an integer as the sum of triangular numbers
498
622Riffle Shuffles
1521
623Lambda Count
284
624Two heads are better than one
544
625Gcd sum
519
626Counting Binary Matrices
204
627Counting products
219
628Open chess positions
704
629Scatterstone Nim
214
630Crossed lines
872
631Constrained Permutations
179
632Square prime factors
411
633Square prime factors II
289
634Numbers of the form $a^2b^3$
529
635Subset sums
299
636Restricted Factorisations
153
637Flexible digit sum
287
638Weighted lattice paths
330
639Summing a multiplicative function
214
640Shut the Box
302
641A Long Row of Dice
395
642Sum of largest prime factors
311
6432-Friendly
510
644Squares on the line
138
645Every Day is a Holiday
187
646Bounded Divisors
247
647Linear Transformations of Polygonal Numbers
374
648Skipping Squares
248
649Low-Prime Chessboard Nim
347
650Divisors of Binomial Product
1354