Prove that there exist infinitely many non prime positive integers $n$ such that $7^{n-1} - 3^{n-1}$ is divisible by $n$. LĂȘ Anh Vinh
Source: 2015 Saudi Arabia BMO TST II p4
Tags: divides, divisible, number theory
Prove that there exist infinitely many non prime positive integers $n$ such that $7^{n-1} - 3^{n-1}$ is divisible by $n$. LĂȘ Anh Vinh