Duffin–Schaeffer theorem
The Koukoulopoulos–Maynard theorem, historically known as the Duffin–Schaeffer conjecture, is a theorem in mathematics, specifically Diophantine approximation. It was proposed as a conjecture by R. J. Duffin and A. C. Schaeffer in 1941 and proven in 2019 by Dimitris Koukoulopoulos and James Maynard.