MathDB
Math Prize 2013 Problem 19

Source:

September 10, 2013
number theoryrelatively prime

Problem Statement

If nn is a positive integer, let ϕ(n)\phi(n) be the number of positive integers less than or equal to nn that are relatively prime to nn. Compute the value of the infinite sum ∑n=1∞ϕ(n)2n9n−2n . \sum_{n=1}^\infty \frac{\phi(n) 2^n}{9^n - 2^n} \, .
Back to ProblemsView on AoPS