中文

Restricted 132-Dumont permutations

组合数学 2007-05-23 v2

摘要

A permutation π\pi is said to be {\em Dumont permutations of the first kind} if each even integer in π\pi must be followed by a smaller integer, and each odd integer is either followed by a larger integer or is the last element of π\pi (see, for example, \cite{Z}). In \cite{D} Dumont showed that certain classes of permutations on nn letters are counted by the Genocchi numbers. In particular, Dumont showed that the (n+1)(n+1)st Genocchi number is the number of Dummont permutations of the first kind on 2n2n letters. In this paper we study the number of Dumont permutations of the first kind on nn letters avoiding the pattern 132 and avoiding (or containing exactly once) an arbitrary pattern on kk letters. In several interesting cases the generating function depends only on kk.

关键词

引用

@article{arxiv.math/0209379,
  title  = {Restricted 132-Dumont permutations},
  author = {T. Mansour},
  journal= {arXiv preprint arXiv:math/0209379},
  year   = {2007}
}

备注

12 pages