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Problems Archives

The problems archives table shows problems 1 to 688. 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
1629
602Product of Head Counts
385
603Substring sums of prime concatenations
330
604Convex path in square
420
605Pairwise Coin-Tossing Game
669
606Gozinta Chains II
308
607Marsh Crossing
1378
608Divisor Sums
253
609π sequences
714
610Roman Numerals II
455
611Hallway of square steps
267
612Friend numbers
522
613Pythagorean Ant
1418
614Special partitions 2
256
615The millionth number with at least one million prime factors
479
616Creative numbers
396
617Mirror Power Sequence
320
618Numbers with a given prime factor sum
784
619Square subsets
330
620Planetary Gears
153
621Expressing an integer as the sum of triangular numbers
448
622Riffle Shuffles
1317
623Lambda Count
264
624Two heads are better than one
474
625Gcd sum
429
626Counting Binary Matrices
181
627Counting products
198
628Open chess positions
620
629Scatterstone Nim
194
630Crossed lines
759
631Constrained Permutations
164
632Square prime factors
354
633Square prime factors II
250
634Numbers of the form $a^2b^3$
461
635Subset sums
251
636Restricted Factorisations
131
637Flexible digit sum
252
638Weighted lattice paths
289
639Summing a multiplicative function
165
640Shut the Box
270
641A Long Row of Dice
333
642Sum of largest prime factors
274
6432-Friendly
412
644Squares on the line
128
645Every Day is a Holiday
158
646Bounded Divisors
217
647Linear Transformations of Polygonal Numbers
324
648Skipping Squares
223
649Low-Prime Chessboard Nim
288
650Divisors of Binomial Product
1010