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Problems Archives

The problems archives table shows problems 1 to 679. 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
501Eight Divisors
1059
502Counting Castles
213
503Compromise or persist
259
504Square on the Inside
2565
505Bidirectional Recurrence
168
506Clock sequence
727
507Shortest Lattice Vector
167
508Integers in base i-1
178
509Divisor Nim
463
510Tangent Circles
848
511Sequences with nice divisibility properties
340
512Sums of totients of powers
1227
513Integral median
254
514Geoboard Shapes
174
515Dissonant Numbers
374
5165-smooth totients
1277
517A real recursion
386
518Prime triples and geometric sequences
1313
519Tricoloured Coin Fountains
289
520Simbers
321
521Smallest prime factor
612
522Hilbert's Blackout
200
523First Sort I
788
524First Sort II
167
525Rolling Ellipse
392
526Largest prime factors of consecutive numbers
254
527Randomized Binary Search
597
528Constrained Sums
223
52910-substrings
181
530GCD of Divisors
349
531Chinese leftovers
898
532Nanobots on Geodesics
242
533Minimum values of the Carmichael function
261
534Weak Queens
238
535Fractal Sequence
236
536Modulo power identity
226
537Counting tuples
487
538Maximum quadrilaterals
265
539Odd elimination
655
540Counting primitive Pythagorean triples
484
541Divisibility of Harmonic Number Denominators
151
542Geometric Progression with Maximum Sum
176
543Prime-Sum Numbers
552
544Chromatic Conundrum
183
545Faulhaber's Formulas
414
546The Floor's Revenge
175
547Distance of random points within hollow square laminae
164
548Gozinta Chains
486
549Divisibility of factorials
2227
550Divisor game
262