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Problems Archives

The problems archives table shows problems 1 to 667. 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
366
552Chinese leftovers II
318
553Power sets of power sets
157
554Centaurs on a chess board
162
555McCarthy 91 function
545
556Squarefree Gaussian Integers
168
557Cutting triangles
229
558Irrational base
184
559Permuted Matrices
128
560Coprime Nim
220
561Divisor Pairs
589
562Maximal perimeter
143
563Robot Welders
252
564Maximal polygons
185
565Divisibility of sum of divisors
474
566Cake Icing Puzzle
107
567Reciprocal games I
204
568Reciprocal games II
200
569Prime Mountain Range
309
570Snowflakes
213
571Super Pandigital Numbers
825
572Idempotent matrices
259
573Unfair race
153
574Verifying Primes
203
575Wandering Robots
431
576Irrational jumps
180
577Counting hexagons
1191
578Integers with decreasing prime powers
168
579Lattice points in lattice cubes
108
580Squarefree Hilbert numbers
173
58147-smooth triangular numbers
647
582Nearly isosceles 120 degree triangles
239
583Heron Envelopes
291
584Birthday Problem Revisited
128
585Nested square roots
117
586Binary Quadratic Form
173
587Concave triangle
2308
588Quintinomial coefficients
337
589Poohsticks Marathon
135
590Sets with a given Least Common Multiple
192
591Best Approximations by Quadratic Integers
132
592Factorial trailing digits 2
219
593Fleeting Medians
396
594Rhombus Tilings
145
595Incremental Random Sort
479
596Number of lattice points in a hyperball
272
597Torpids
114
598Split Divisibilities
375
599Distinct Colourings of a Rubik's Cube
232
600Integer sided equiangular hexagons
458