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Problems Archives

The problems archives table shows problems 1 to 682. 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
1615
602Product of Head Counts
380
603Substring sums of prime concatenations
330
604Convex path in square
417
605Pairwise Coin-Tossing Game
662
606Gozinta Chains II
302
607Marsh Crossing
1360
608Divisor Sums
251
609π sequences
700
610Roman Numerals II
450
611Hallway of square steps
264
612Friend numbers
513
613Pythagorean Ant
1390
614Special partitions 2
253
615The millionth number with at least one million prime factors
470
616Creative numbers
391
617Mirror Power Sequence
318
618Numbers with a given prime factor sum
766
619Square subsets
319
620Planetary Gears
153
621Expressing an integer as the sum of triangular numbers
440
622Riffle Shuffles
1297
623Lambda Count
259
624Two heads are better than one
471
625Gcd sum
421
626Counting Binary Matrices
180
627Counting products
197
628Open chess positions
611
629Scatterstone Nim
191
630Crossed lines
737
631Constrained Permutations
163
632Square prime factors
347
633Square prime factors II
250
634Numbers of the form $a^2b^3$
448
635Subset sums
248
636Restricted Factorisations
127
637Flexible digit sum
250
638Weighted lattice paths
284
639Summing a multiplicative function
164
640Shut the Box
270
641A Long Row of Dice
323
642Sum of largest prime factors
268
6432-Friendly
397
644Squares on the line
124
645Every Day is a Holiday
154
646Bounded Divisors
212
647Linear Transformations of Polygonal Numbers
318
648Skipping Squares
220
649Low-Prime Chessboard Nim
279
650Divisors of Binomial Product
954