Recursions for Excedance number in some permutations groups
组合数学
2008-06-03 v2 群论
摘要
The excedance number for S_n is known to have an Eulerian distribution. Nevertheless, the classical proof uses descents rather than excedances. We present a direct recursive proof which seems to be folklore and extend it to the colored permutation groups G_r,n. The generalized recursion yields some interesting connection to Stirling numbers of the second kind. We also show some logconcavity result concerning a variant of the excedance number. Finally, we show that the generating function of the excedance number defined on G_r,n is symmetric.
引用
@article{arxiv.math/0702452,
title = {Recursions for Excedance number in some permutations groups},
author = {Eli Bagno and David Garber and Toufik Mansour and Robert Shwartz},
journal= {arXiv preprint arXiv:math/0702452},
year = {2008}
}
备注
14 pages, no figures; revised version with new results