Herglotz–Zagier function

In mathematics, the Herglotz–Zagier function, named after Gustav Herglotz and Don Zagier, is the function

${\displaystyle F(x)=\sum _{n=1}^{\infty }\left\{{\frac {\Gamma ^{\prime }(nx)}{\Gamma (nx)}}-\log(nx)\right\}{\frac {1}{n}}.}$

introduced by Zagier (1975) who used it to obtain a Kronecker limit formula for real quadratic fields.