MathDB
2016 LMT Individual #21

Source:

April 10, 2016

Problem Statement

Let SS be the set of positive integers nn such that 3⋅φ(n)=n,3\cdot \varphi (n)=n, where φ(n)\varphi (n) is the number of positive integers k≤nk\leq n such that gcd⁡(k,n)=1\gcd (k, n)=1. Find ∑n∈S 1n.\sum_{n\in S} \, \frac{1}{n}.
Proposed by Nathan Ramesh
Back to ProblemsView on AoPS