For other values of , is defined by analytic
continuation. This is the notation used in Erdélyi et al. (1953a, p. 27).
Lerch (1887) used
The Hurwitz zeta function (§25.11) and the
polylogarithm (§25.12(ii)) are special
With the conditions of (25.14.1) and ,
For these and further properties see Erdélyi et al. (1953a, pp. 27–31).