Apéry's constant

Apéry's constant is a mathematical constant, defined as the infinite sum of the reciprocals of the cubes of the positive integers. In symbols,

${\displaystyle {\begin{aligned}\zeta (3)&=\sum _{n=1}^{\infty }{\frac {1}{n^{3}}}\end{aligned}}}$

where ζ is the Riemann zeta function. It has an approximate value of

ζ(3) ≈ 1.202056903159594285399738161511449990764986292… (sequence A002117 in the OEIS).

It is named after Roger Apéry, who proved that it is an irrational number.