English

Restricted single or double signed patterns

Combinatorics 2007-05-23 v1

Abstract

Let Enr={[τ]a=(τ1(a1),...,τn(an))τSn, 1air}E_n^r=\{[\tau]_a=(\tau_1^{(a_1)},...,\tau_n^{(a_n)})| \tau\in S_n,\ 1\leq a_i\leq r\} be the set of all signed permutations on the symbols 1,2,...,n with signs 1,2,...,r. We prove, for every 2-letter signed pattern [τ]a[\tau]_a, that the number of [τ]a[\tau]_a-avoiding signed permutations in EnrE_n^r is given by the formula j=0nj!(r1)j(nj)2\sum\limits_{j=0}^n j!(r-1)^j{n\choose j}^2. Also we prove that there are only one Wilf class for r=1, four Wilf classes for r=2, and six Wilf classes for r3r\geq 3.

Cite

@article{arxiv.math/0011072,
  title  = {Restricted single or double signed patterns},
  author = {T. Mansour},
  journal= {arXiv preprint arXiv:math/0011072},
  year   = {2007}
}

Comments

13 pages, 1 table, 1 figure