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Problems Archives

The problems archives table shows problems 1 to 646. 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
349
552Chinese leftovers II
297
553Power sets of power sets
144
554Centaurs on a chess board
149
555McCarthy 91 function
515
556Squarefree Gaussian Integers
159
557Cutting triangles
219
558Irrational base
172
559Permuted Matrices
122
560Coprime Nim
199
561Divisor Pairs
561
562Maximal perimeter
137
563Robot Welders
240
564Maximal polygons
177
565Divisibility of sum of divisors
452
566Cake Icing Puzzle
102
567Reciprocal games I
189
568Reciprocal games II
187
569Prime Mountain Range
297
570Snowflakes
198
571Super Pandigital Numbers
783
572Idempotent matrices
243
573Unfair race
141
574Verifying Primes
194
575Wandering Robots
402
576Irrational jumps
169
577Counting hexagons
1098
578Integers with decreasing prime powers
154
579Lattice points in lattice cubes
101
580Squarefree Hilbert numbers
167
58147-smooth triangular numbers
613
582Nearly isosceles 120 degree triangles
227
583Heron Envelopes
275
584Birthday Problem Revisited
121
585Nested square roots
104
586Binary Quadratic Form
162
587Concave triangle
2098
588Quintinomial coefficients
328
589Poohsticks Marathon
129
590Sets with a given Least Common Multiple
183
591Best Approximations by Quadratic Integers
123
592Factorial trailing digits 2
208
593Fleeting Medians
367
594Rhombus Tilings
138
595Incremental Random Sort
450
596Number of lattice points in a hyperball
259
597Torpids
108
598Split Divisibilities
349
599Distinct Colourings of a Rubik's Cube
220
600Integer sided equiangular hexagons
431