The Lindelöf-Wirtinger expansion of the Lerch transcendent function implies, as a limiting case, Hurwitz's formula for the eponymous zeta function. A generalized form of Möbius inversion applies to the Lindelöf-Wirtinger expansion and also implies an inversion formula for the Hurwitz zeta function as a limiting case. The inverted formulas involve the dynamical system of rotations of the circle and yield an arithmetical functional equation.see [8, §1.11, p. 27] or [2, §25.14], for example. Logarithms and complex powers are always assumed to be principal. If |λ| < 1, then for any s ∈ C, the series converges uniformly in z over C\(−∞, 0], thus defining a holomorphic function of z in this region. If |λ| = 1, then the series converges in this same region provided Re s > 1. The value λ = 0 is considered trivial since it yields Φ(0, s, z) = z −s , and thus is usually excluded. There are multiple ways of defining analytic continuations of Φ in each parameter. This function, defined by Mathias Lerch in 1887 in his paper [11], includes as special cases of the parameters the Hurwitz and Riemann zeta functions and the polylogarithms, among others, and has applications ranging from number theory to physics. It is often used to obtain functional identities; see, for instance, [3,7,9,15].One often extends the domain to z ∈ C \ {0, −1, −2, . . . } by including the branch discontinuity of the principal argument. In addition, in this paper we shall only be considering s ∈ C with Re s < 0, in which case the summand (k + z) −s (with k ∈ N) in (1.1) continuously extends to z = −k by defining 0 −s = 0. Thus for Re s < 0 we can define Φ(λ, s, z) for all z ∈ C. For the parameter s, we shall often denote σ = Re s. Also, we shall use the notation C * = C \ {0}.