The harmonic polylogarithm is an iterated
integral with indices
. It can be expressed
using the generalized polylogarithm
as
where
is the number of indices equal to 1. Equivalently, its integration kernels for indices
, 0, and 1 are
,
, and
, respectively. For
, the one-index cases are
,
,
and
(Remiddi and Vermaseren 2000).
The harmonic polylogarithm is implemented in the Wolfram Language as HarmonicPolyLog[{a1, ..., ak}, z].