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Problems Archives

The problems archives table shows problems 1 to 666. 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
359
552Chinese leftovers II
309
553Power sets of power sets
151
554Centaurs on a chess board
160
555McCarthy 91 function
537
556Squarefree Gaussian Integers
167
557Cutting triangles
225
558Irrational base
182
559Permuted Matrices
127
560Coprime Nim
213
561Divisor Pairs
577
562Maximal perimeter
140
563Robot Welders
244
564Maximal polygons
183
565Divisibility of sum of divisors
464
566Cake Icing Puzzle
108
567Reciprocal games I
200
568Reciprocal games II
195
569Prime Mountain Range
304
570Snowflakes
207
571Super Pandigital Numbers
808
572Idempotent matrices
252
573Unfair race
149
574Verifying Primes
200
575Wandering Robots
419
576Irrational jumps
176
577Counting hexagons
1162
578Integers with decreasing prime powers
165
579Lattice points in lattice cubes
106
580Squarefree Hilbert numbers
171
58147-smooth triangular numbers
634
582Nearly isosceles 120 degree triangles
235
583Heron Envelopes
284
584Birthday Problem Revisited
127
585Nested square roots
111
586Binary Quadratic Form
170
587Concave triangle
2241
588Quintinomial coefficients
334
589Poohsticks Marathon
131
590Sets with a given Least Common Multiple
190
591Best Approximations by Quadratic Integers
127
592Factorial trailing digits 2
212
593Fleeting Medians
386
594Rhombus Tilings
141
595Incremental Random Sort
472
596Number of lattice points in a hyperball
265
597Torpids
113
598Split Divisibilities
361
599Distinct Colourings of a Rubik's Cube
227
600Integer sided equiangular hexagons
444