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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
551Sum of digits sequence
390
552Chinese leftovers II
348
553Power sets of power sets
171
554Centaurs on a chess board
180
555McCarthy 91 function
568
556Squarefree Gaussian Integers
185
557Cutting triangles
242
558Irrational base
195
559Permuted Matrices
140
560Coprime Nim
237
561Divisor Pairs
614
562Maximal perimeter
153
563Robot Welders
266
564Maximal polygons
197
565Divisibility of sum of divisors
501
566Cake Icing Puzzle
118
567Reciprocal games I
223
568Reciprocal games II
216
569Prime Mountain Range
327
570Snowflakes
227
571Super Pandigital Numbers
876
572Idempotent matrices
274
573Unfair race
161
574Verifying Primes
218
575Wandering Robots
453
576Irrational jumps
187
577Counting hexagons
1274
578Integers with decreasing prime powers
182
579Lattice points in lattice cubes
117
580Squarefree Hilbert numbers
186
58147-smooth triangular numbers
678
582Nearly isosceles 120 degree triangles
254
583Heron Envelopes
308
584Birthday Problem Revisited
146
585Nested square roots
128
586Binary Quadratic Form
181
587Concave triangle
2473
588Quintinomial coefficients
352
589Poohsticks Marathon
151
590Sets with a given Least Common Multiple
205
591Best Approximations by Quadratic Integers
144
592Factorial trailing digits 2
233
593Fleeting Medians
426
594Rhombus Tilings
152
595Incremental Random Sort
512
596Number of lattice points in a hyperball
287
597Torpids
121
598Split Divisibilities
391
599Distinct Colourings of a Rubik's Cube
239
600Integer sided equiangular hexagons
485