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Problems Archives

The problems archives table shows problems 1 to 713. 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
400
552Chinese leftovers II
367
553Power sets of power sets
177
554Centaurs on a chess board
183
555McCarthy 91 function
590
556Squarefree Gaussian Integers
192
557Cutting triangles
247
558Irrational base
207
559Permuted Matrices
154
560Coprime Nim
245
561Divisor Pairs
647
562Maximal perimeter
158
563Robot Welders
284
564Maximal polygons
201
565Divisibility of sum of divisors
522
566Cake Icing Puzzle
129
567Reciprocal games I
229
568Reciprocal games II
220
569Prime Mountain Range
344
570Snowflakes
238
571Super Pandigital Numbers
933
572Idempotent matrices
281
573Unfair race
168
574Verifying Primes
230
575Wandering Robots
482
576Irrational jumps
198
577Counting hexagons
1339
578Integers with decreasing prime powers
188
579Lattice points in lattice cubes
128
580Squarefree Hilbert numbers
198
58147-smooth triangular numbers
719
582Nearly isosceles 120 degree triangles
268
583Heron Envelopes
322
584Birthday Problem Revisited
157
585Nested square roots
133
586Binary Quadratic Form
185
587Concave triangle
2636
588Quintinomial coefficients
360
589Poohsticks Marathon
158
590Sets with a given Least Common Multiple
222
591Best Approximations by Quadratic Integers
160
592Factorial trailing digits 2
238
593Fleeting Medians
451
594Rhombus Tilings
159
595Incremental Random Sort
535
596Number of lattice points in a hyperball
299
597Torpids
128
598Split Divisibilities
410
599Distinct Colourings of a Rubik's Cube
249
600Integer sided equiangular hexagons
517