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Problems Archives

  • Problem 666 will be accessible in 1 day, 14 hours, 19 minutes (Saturday, 20th April 2019, 01:00 pm)

The problems archives table shows problems 1 to 655. 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
357
552Chinese leftovers II
305
553Power sets of power sets
148
554Centaurs on a chess board
155
555McCarthy 91 function
526
556Squarefree Gaussian Integers
159
557Cutting triangles
221
558Irrational base
177
559Permuted Matrices
123
560Coprime Nim
202
561Divisor Pairs
567
562Maximal perimeter
138
563Robot Welders
240
564Maximal polygons
179
565Divisibility of sum of divisors
455
566Cake Icing Puzzle
104
567Reciprocal games I
195
568Reciprocal games II
191
569Prime Mountain Range
297
570Snowflakes
204
571Super Pandigital Numbers
796
572Idempotent matrices
245
573Unfair race
147
574Verifying Primes
197
575Wandering Robots
410
576Irrational jumps
173
577Counting hexagons
1135
578Integers with decreasing prime powers
157
579Lattice points in lattice cubes
104
580Squarefree Hilbert numbers
168
58147-smooth triangular numbers
619
582Nearly isosceles 120 degree triangles
232
583Heron Envelopes
279
584Birthday Problem Revisited
124
585Nested square roots
107
586Binary Quadratic Form
168
587Concave triangle
2174
588Quintinomial coefficients
330
589Poohsticks Marathon
129
590Sets with a given Least Common Multiple
188
591Best Approximations by Quadratic Integers
125
592Factorial trailing digits 2
213
593Fleeting Medians
375
594Rhombus Tilings
138
595Incremental Random Sort
461
596Number of lattice points in a hyperball
262
597Torpids
112
598Split Divisibilities
354
599Distinct Colourings of a Rubik's Cube
224
600Integer sided equiangular hexagons
441