Find all positive integers $n$ such that all prime factors of $2^n-1$ are less than or equal to $7$.
Problem
Source: 2023 Argentina OMA Finals L3 p2 - repost for forum collection
Tags: number theory, prime factors
Source: 2023 Argentina OMA Finals L3 p2 - repost for forum collection
Tags: number theory, prime factors
Find all positive integers $n$ such that all prime factors of $2^n-1$ are less than or equal to $7$.