### Riemann Zeta Function

The Riemann zeta function is defined by the infinite sum \zeta(s) = \sum_{k=1}^\infty k^{-s}.

Function: double gsl_sf_zeta_int (int n)
Function: int gsl_sf_zeta_int_e (int n, gsl_sf_result * result)
  These routines compute the Riemann zeta function \zeta(n) for integer n, n \ne 1.

Function: double gsl_sf_zeta (double s)
Function: int gsl_sf_zeta_e (double s, gsl_sf_result * result)
  These routines compute the Riemann zeta function \zeta(s) for arbitrary s, s \ne 1.