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April 7, 2005
modular arithmeticnumber theory proposednumber theory

Problem Statement

Let nn be a positive integer. SS is the set of nonnegative integers aa such that 1<a<n1<a<n and aa−1−1a^{a-1}-1 is divisible by nn. Prove that if S={n−1}S=\{ n-1 \} then n=2pn=2p where pp is a prime number.
Mihai Cipu and Nicolae Ciprian Bonciocat
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