Function: lerchphi
Section: transcendental
C-Name: lerchphi
Prototype: GGGp
Help: lerchphi(z,s,a): Lerch transcendent equal to sum for n >= 0 of
 z^n / (n+a)^s for reasonable values of the arguments.
Doc: Lerch transcendent $\Phi(z,s,a)=\sum_{n\ge0}z^{n}(n+a)^{-s}$ and
 analytically continued, for reasonable values of the arguments.
