Srinivasa Iyengar Ramanujan, Indian mathematician (Erode, Tamil Nadu 22 December 1887 – Chetput, Madras 26 April 1920)

Discovered mock theta functions (1920)

Imagined a method for calculating the value of π number

Derived a formula for determination of quantity of primes lower than a given previously number  

Discovered properties of congruency, symmetry and other kinds of relations

First to discover some arithmetical properties of p(n), the number of unrestricted partitions of n 

EPONYMY

Hardy-Ramanujan-Littlewood circle method

Roger-Ramanujan identities (1913)

Rogers-Ramanujan continuous fraction

Hardy-Ramanujan number

Ramanujan conjecture

Ramanujan congruence

Ramanujan theta function  

Landau-Ramanujan function   

Landau-Ramanujan constant

Ramanujan primes (1919)

Ramanujan sum (1918)

Ramanujan summation

Ramanujan-Soldner constant  

Ramanujan expansion (1918)

Ramanujan-Eisenstein series  

Ramanujan-Sato series  

Ramanujan-Dirichlet series  

Hardy-Ramanujan series

Hardy-Ramanujan-Rademacher asymptotic partition formula (1918);

Hardy-Ramanujan inequalities  

Ramanujan graphs  

Ramanujan-Petersson conjecture  

Ramanujan constant  

Ramanujan tau function or Ramanujan congruences (1916)

Ramanujan-Nagell equation (1913)

Ramanujan-Skolem theorem  

Dougall-Ramanujan identity  

Nielsen-Ramanujan constant