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Problems Archives

The problems archives table shows problems 1 to 699. 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
1664
602Product of Head Counts
398
603Substring sums of prime concatenations
335
604Convex path in square
424
605Pairwise Coin-Tossing Game
681
606Gozinta Chains II
311
607Marsh Crossing
1406
608Divisor Sums
255
609π sequences
739
610Roman Numerals II
471
611Hallway of square steps
273
612Friend numbers
533
613Pythagorean Ant
1446
614Special partitions 2
257
615The millionth number with at least one million prime factors
487
616Creative numbers
408
617Mirror Power Sequence
325
618Numbers with a given prime factor sum
802
619Square subsets
337
620Planetary Gears
154
621Expressing an integer as the sum of triangular numbers
462
622Riffle Shuffles
1357
623Lambda Count
268
624Two heads are better than one
490
625Gcd sum
441
626Counting Binary Matrices
183
627Counting products
202
628Open chess positions
637
629Scatterstone Nim
194
630Crossed lines
782
631Constrained Permutations
165
632Square prime factors
369
633Square prime factors II
258
634Numbers of the form $a^2b^3$
476
635Subset sums
260
636Restricted Factorisations
137
637Flexible digit sum
263
638Weighted lattice paths
303
639Summing a multiplicative function
177
640Shut the Box
277
641A Long Row of Dice
350
642Sum of largest prime factors
282
6432-Friendly
439
644Squares on the line
132
645Every Day is a Holiday
162
646Bounded Divisors
223
647Linear Transformations of Polygonal Numbers
340
648Skipping Squares
226
649Low-Prime Chessboard Nim
302
650Divisors of Binomial Product
1073