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Problems Archives

The problems archives table shows problems 1 to 641. 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
971
502Counting Castles
197
503Compromise or persist
240
504Square on the Inside
2307
505Bidirectional Recurrence
154
506Clock sequence
675
507Shortest Lattice Vector
148
508Integers in base i-1
162
509Divisor Nim
416
510Tangent Circles
794
511Sequences with nice divisibility properties
311
512Sums of totients of powers
1125
513Integral median
234
514Geoboard Shapes
162
515Dissonant Numbers
340
5165-smooth totients
1140
517A real recursion
360
518Prime triples and geometric sequences
1180
519Tricoloured Coin Fountains
263
520Simbers
297
521Smallest prime factor
563
522Hilbert's Blackout
181
523First Sort I
701
524First Sort II
158
525Rolling Ellipse
367
526Largest prime factors of consecutive numbers
230
527Randomized Binary Search
549
528Constrained Sums
203
52910-substrings
155
530GCD of Divisors
300
531Chinese leftovers
805
532Nanobots on Geodesics
224
533Minimum values of the Carmichael function
242
534Weak Queens
217
535Fractal Sequence
215
536Modulo power identity
204
537Counting tuples
428
538Maximum quadrilaterals
245
539Odd elimination
614
540Counting primitive Pythagorean triples
438
541Divisibility of Harmonic Number Denominators
141
542Geometric Progression with Maximum Sum
163
543Prime-Sum Numbers
495
544Chromatic Conundrum
158
545Faulhaber's Formulas
374
546The Floor's Revenge
161
547Distance of random points within hollow square laminae
154
548Gozinta Chains
438
549Divisibility of factorials
2004
550Divisor game
227