## Inversion of some series of free quasi-symmetric functions

##### Authors
Hivert, Florent
Novelli, Jean-Christophe
Thibon, Jean-Yves
##### Description
We give a combinatorial formula for the inverses of the alternating sums of free quasi-symmetric functions of the form F_{\omega(I)} where I runs over compositions with parts in a prescribed set C. This proves in particular three special cases (no restriction, even parts, and all parts equal to 2) which were conjectured by B. C. V. Ung in [Proc. FPSAC'98, Toronto].
Comment: 6 pages
##### Keywords
Mathematics - Combinatorics