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Problems


IDDescription / Title
401
Sum of squares of divisors
402
Integer-valued polynomials
403
Lattice points enclosed by parabola and line
404
Crisscross Ellipses
405
A rectangular tiling
406
Guessing Game
407
Idempotents
408
Admissible paths through a grid
409
Nim Extreme
410
Circle and tangent line
411
Uphill paths
412
Gnomon numbering
413
One-child Numbers
414
Kaprekar constant
415
Titanic sets
416
A frog's trip
417
Reciprocal cycles II
418
Factorisation triples
419
Look and say sequence
420
2x2 positive integer matrix
421
Prime factors of n15+1
422
Sequence of points on a hyperbola
423
Consecutive die throws
424
Kakuro
425
Prime connection
426
Box-ball system
427
n-sequences
428
Necklace of circles
429
Sum of squares of unitary divisors
430
Range flips
431
Square Space Silo
432
Totient sum
433
Steps in Euclid's algorithm
434
Rigid graphs
435
Polynomials of Fibonacci numbers
436
Unfair wager
437
Fibonacci primitive roots
438
Integer part of polynomial equation's solutions
439
Sum of sum of divisors
440
GCD and Tiling
441
The inverse summation of coprime couples
442
Eleven-free integers
443
GCD sequence
444
The Roundtable Lottery
445
Retractions A
446
Retractions B
447
Retractions C
448
Average least common multiple
449
Chocolate covered candy
450
Hypocycloid and Lattice points