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Problems Archives

The problems archives table shows problems 1 to 726. 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.


ID

Description / TitleSolved By
501Eight Divisors
1181
502Counting Castles
244
503Compromise or persist
277
504Square on the Inside
2787
505Bidirectional Recurrence
187
506Clock sequence
777
507Shortest Lattice Vector
185
508Integers in base i-1
208
509Divisor Nim
511
510Tangent Circles
921
511Sequences with nice divisibility properties
369
512Sums of totients of powers
1346
513Integral median
275
514Geoboard Shapes
193
515Dissonant Numbers
414
5165-smooth totients
1400
517A real recursion
414
518Prime triples and geometric sequences
1450
519Tricoloured Coin Fountains
310
520Simbers
357
521Smallest prime factor
668
522Hilbert's Blackout
233
523First Sort I
877
524First Sort II
187
525Rolling Ellipse
441
526Largest prime factors of consecutive numbers
272
527Randomized Binary Search
651
528Constrained Sums
243
52910-substrings
213
530GCD of Divisors
387
531Chinese leftovers
1000
532Nanobots on Geodesics
273
533Minimum values of the Carmichael function
287
534Weak Queens
259
535Fractal Sequence
253
536Modulo power identity
245
537Counting tuples
543
538Maximum quadrilaterals
290
539Odd elimination
723
540Counting primitive Pythagorean triples
542
541Divisibility of Harmonic Number Denominators
175
542Geometric Progression with Maximum Sum
199
543Prime-Sum Numbers
603
544Chromatic Conundrum
210
545Faulhaber's Formulas
460
546The Floor's Revenge
201
547Distance of random points within hollow square laminae
182
548Gozinta Chains
534
549Divisibility of factorials
2439
550Divisor game
299