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p is a divisor of 5^m7^n-1

Source: 2021 Dutch IMO TST 3.4

December 28, 2021
number theorydivisor

Problem Statement

Let p>10p > 10 be prime. Prove that there are positive integers mm and nn with m+n<pm + n < p exist for which pp is a divisor of 5m7nāˆ’15^m7^n-1.