Ramanujan–Petersson conjecture
In mathematics, the Ramanujan-Petersson conjecture is a conjecture concerning the growth rate of coefficients of modular forms and more generally, automorphic forms. The name of the conjecture comes from Srinivasa Ramanujan, who proposed it for Ramanujan tau function, and Hans Petersson, who generalized it for coefficients of modular forms.
Source: Wikipedia — Ramanujan–Petersson conjecture (CC BY-SA 4.0)