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Problems Archives

  • Problem 680 will be accessible in 19 hours, 3 minutes (Sunday, 22nd September 2019, 04:00 am)

The problems archives table shows problems 1 to 669. 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
401Sum of squares of divisors
2111
402Integer-valued polynomials
315
403Lattice points enclosed by parabola and line
300
404Crisscross Ellipses
269
405A rectangular tiling
486
406Guessing Game
315
407Idempotents
2007
408Admissible paths through a grid
464
409Nim Extreme
377
410Circle and tangent line
233
411Uphill paths
520
412Gnomon numbering
391
413One-child Numbers
318
414Kaprekar constant
230
415Titanic sets
246
416A frog's trip
237
417Reciprocal cycles II
690
418Factorisation triples
562
419Look and say sequence
407
4202x2 positive integer matrix
351
421Prime factors of n15+1
519
422Sequence of points on a hyperbola
227
423Consecutive die throws
387
424Kakuro
319
425Prime connection
1191
426Box-ball system
209
427n-sequences
232
428Necklace of circles
201
429Sum of squares of unitary divisors
2149
430Range flips
719
431Square Space Silo
499
432Totient sum
390
433Steps in Euclid's algorithm
407
434Rigid graphs
281
435Polynomials of Fibonacci numbers
862
436Unfair wager
369
437Fibonacci primitive roots
630
438Integer part of polynomial equation's solutions
233
439Sum of sum of divisors
293
440GCD and Tiling
299
441The inverse summation of coprime couples
295
442Eleven-free integers
326
443GCD sequence
913
444The Roundtable Lottery
248
445Retractions A
289
446Retractions B
279
447Retractions C
207
448Average least common multiple
259
449Chocolate covered candy
741
450Hypocycloid and Lattice points
161