Catalan's constant

Named after French and Belgian mathematician Eugène Charles Catalan.

Catalan's constant

1. (mathematics) The number ${\displaystyle G=\beta (2)=\sum _{n=0}^{\infty }{\frac {(-1)^{n}}{(2n+1)^{2}}}={\frac {1}{1^{2}}}-{\frac {1}{3^{2}}}+{\frac {1}{5^{2}}}-{\frac {1}{7^{2}}}+{\frac {1}{9^{2}}}-\cdots }$, where β is the Dirichlet beta function, with a value of approximately 0.915965594177…