Apéry's constant

Etymology
Named after French mathematician Roger Apéry who proved in 1978 that it is an irrational number.

Proper noun

 * 1)  The number $$ \zeta(3)=\sum_{n=1}^\infty \frac{1}{n^3}$$, where $ζ$ is the Riemann zeta function, with a value of approximately 1.2020569…