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Problems Archives

  • Problem 684 will be accessible in 16 hours, 14 minutes (Saturday, 19th October 2019, 04:00 pm)
  • Problem 685 will be accessible in 16 hours, 14 minutes (Saturday, 19th October 2019, 04:00 pm)

The problems archives table shows problems 1 to 673. 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
373
552Chinese leftovers II
326
553Power sets of power sets
161
554Centaurs on a chess board
168
555McCarthy 91 function
555
556Squarefree Gaussian Integers
172
557Cutting triangles
232
558Irrational base
187
559Permuted Matrices
131
560Coprime Nim
226
561Divisor Pairs
600
562Maximal perimeter
148
563Robot Welders
253
564Maximal polygons
188
565Divisibility of sum of divisors
481
566Cake Icing Puzzle
110
567Reciprocal games I
210
568Reciprocal games II
205
569Prime Mountain Range
316
570Snowflakes
217
571Super Pandigital Numbers
834
572Idempotent matrices
261
573Unfair race
153
574Verifying Primes
207
575Wandering Robots
438
576Irrational jumps
183
577Counting hexagons
1222
578Integers with decreasing prime powers
173
579Lattice points in lattice cubes
108
580Squarefree Hilbert numbers
178
58147-smooth triangular numbers
661
582Nearly isosceles 120 degree triangles
244
583Heron Envelopes
294
584Birthday Problem Revisited
130
585Nested square roots
121
586Binary Quadratic Form
175
587Concave triangle
2367
588Quintinomial coefficients
341
589Poohsticks Marathon
140
590Sets with a given Least Common Multiple
194
591Best Approximations by Quadratic Integers
133
592Factorial trailing digits 2
224
593Fleeting Medians
401
594Rhombus Tilings
145
595Incremental Random Sort
491
596Number of lattice points in a hyperball
280
597Torpids
113
598Split Divisibilities
379
599Distinct Colourings of a Rubik's Cube
233
600Integer sided equiangular hexagons
466