Dirichlet L-function
From specialfunctionswiki
Let $\chi$ be a Dirichlet character. The Dirichlet $L$-function associated with $\chi$ is $$L(\chi,s)=\displaystyle\sum_n \dfrac{\chi(n)}{n^s} = \displaystyle\prod_{p \hspace{2pt} \mathrm{prime}} \dfrac{1}{1-\chi(p)p^{-s}}.$$
