MathDB
2023 Putnam B5

Source:

December 3, 2023
PutnamPutnam 2023

Problem Statement

Determine which positive integers nn have the following property: For all integers mm that are relatively prime to nn, there exists a permutation π:{1,2,,n}{1,2,,n}\pi:\{1,2, \ldots, n\} \rightarrow\{1,2, \ldots, n\} such that π(π(k))mk(modn)\pi(\pi(k)) \equiv m k(\bmod n) for all k{1,2,,n}k \in\{1,2, \ldots, n\}.