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Problems Archives

The problems archives table shows problems 1 to 713. 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
1725
602Product of Head Counts
412
603Substring sums of prime concatenations
344
604Convex path in square
435
605Pairwise Coin-Tossing Game
705
606Gozinta Chains II
321
607Marsh Crossing
1442
608Divisor Sums
258
609π sequences
767
610Roman Numerals II
482
611Hallway of square steps
275
612Friend numbers
558
613Pythagorean Ant
1491
614Special partitions 2
262
615The millionth number with at least one million prime factors
495
616Creative numbers
419
617Mirror Power Sequence
335
618Numbers with a given prime factor sum
838
619Square subsets
341
620Planetary Gears
158
621Expressing an integer as the sum of triangular numbers
477
622Riffle Shuffles
1403
623Lambda Count
269
624Two heads are better than one
514
625Gcd sum
468
626Counting Binary Matrices
192
627Counting products
208
628Open chess positions
662
629Scatterstone Nim
202
630Crossed lines
810
631Constrained Permutations
171
632Square prime factors
380
633Square prime factors II
270
634Numbers of the form $a^2b^3$
501
635Subset sums
272
636Restricted Factorisations
138
637Flexible digit sum
267
638Weighted lattice paths
317
639Summing a multiplicative function
194
640Shut the Box
282
641A Long Row of Dice
362
642Sum of largest prime factors
292
6432-Friendly
460
644Squares on the line
133
645Every Day is a Holiday
164
646Bounded Divisors
229
647Linear Transformations of Polygonal Numbers
349
648Skipping Squares
233
649Low-Prime Chessboard Nim
312
650Divisors of Binomial Product
1173