olymmath

ISL 2022 N7

    Let kk be a positive integer and let SS be a finite set of odd prime numbers. Prove that there is at most one way (modulo rotation and reflection) to place the elements of SS around a circle such that the product of any two neighbors is of the form x2+x+kx^{2}+x+k for some positive integer xx. (U.S.A.)

    Official text Transcription from NuminaMath olympiads, checked word for word against the official paper. Quoted with source.

    Official text: IMO 2022 Shortlist booklet, page 9.

    Solutions

    Official solution Solution 1 by the IMO Problem Selection Committee

    The terms of the source let olymmath link to this solution but not copy it. Read the solution (IMO official site).

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