Analytic Continuations of Character and Alternating Tornheim Zeta Functions

Abstract

A method developed by Crandall is used to analytically continue character and alternating analogues of a double sum in three complex variables, known as the Tornheim or Mordell–Tornheim–Witten zeta function. We evaluate these functions at triples of nonpositive integer arguments in terms of generalized Bernoulli numbers, and determine those for which a given function is zero. Some special cases are related to tangent numbers.