On a multiple harmonic power series.
Résumé
If $\Li_s$ denotes the polylogarithm of order~$s$, where $s$ is a natural number, and if $z$ belongs to the unit disk, \[ \Li_s {\Bigl({-z\over1\,{-}\,z}\Bigr)} =-\sum _{1\le i_1\le \ldots\le i_s} {z^{i_s}\over i_1i_2\ldots i_s}\;. \] In particular, \[ \sum _{n\ge 1}{\mup {n+1}\over n^s\!}\,= \sum _{1\le i_1\le \ldots\le i_s} {1\over{i_1}\ldots{i_s}\,2^{i_s}}\;. \]