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Problems Archives

The problems archives table shows problems 1 to 667. 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
1021
502Counting Castles
205
503Compromise or persist
249
504Square on the Inside
2454
505Bidirectional Recurrence
160
506Clock sequence
704
507Shortest Lattice Vector
157
508Integers in base i-1
168
509Divisor Nim
446
510Tangent Circles
832
511Sequences with nice divisibility properties
331
512Sums of totients of powers
1183
513Integral median
245
514Geoboard Shapes
167
515Dissonant Numbers
357
5165-smooth totients
1223
517A real recursion
374
518Prime triples and geometric sequences
1258
519Tricoloured Coin Fountains
277
520Simbers
313
521Smallest prime factor
595
522Hilbert's Blackout
189
523First Sort I
750
524First Sort II
162
525Rolling Ellipse
378
526Largest prime factors of consecutive numbers
243
527Randomized Binary Search
580
528Constrained Sums
212
52910-substrings
170
530GCD of Divisors
329
531Chinese leftovers
859
532Nanobots on Geodesics
235
533Minimum values of the Carmichael function
251
534Weak Queens
229
535Fractal Sequence
229
536Modulo power identity
219
537Counting tuples
468
538Maximum quadrilaterals
259
539Odd elimination
642
540Counting primitive Pythagorean triples
464
541Divisibility of Harmonic Number Denominators
148
542Geometric Progression with Maximum Sum
171
543Prime-Sum Numbers
533
544Chromatic Conundrum
169
545Faulhaber's Formulas
400
546The Floor's Revenge
168
547Distance of random points within hollow square laminae
158
548Gozinta Chains
465
549Divisibility of factorials
2145
550Divisor game
240