An almost sharp quantitative version of the Duffin-Schaeffer conjecture

Dimitris Koukoulopoulos, James Maynard, Daodao Yang

We prove a quantitative version of the Duffin-Schaeffer conjecture with an almost sharp error term. Precisely, let $\psi :\mathbb{N}\to [0,1/2]$ be a function such that the series $\sum…