English

Generalized pattern avoidance with additional restrictions

Combinatorics 2007-05-23 v1

Abstract

Babson and Steingr\'{\i}msson introduced generalized permutation patterns that allow the requirement that two adjacent letters in a pattern must be adjacent in the permutation. We consider n-permutations that avoid the generalized pattern 1-32 and whose k rightmost letters form an increasing subword. The number of such permutations is a linear combination of Bell numbers. We find a bijection between these permutations and all partitions of an (n1)(n-1)-element set with one subset marked that satisfy certain additional conditions. Also we find the e.g.f. for the number of permutations that avoid a generalized 3-pattern with no dashes and whose k leftmost or k rightmost letters form either an increasing or decreasing subword. Moreover, we find a bijection between n-permutations that avoid the pattern 132 and begin with the pattern 12 and increasing rooted trimmed trees with n+1 nodes.

Keywords

Cite

@article{arxiv.math/0205215,
  title  = {Generalized pattern avoidance with additional restrictions},
  author = {Sergey Kitaev},
  journal= {arXiv preprint arXiv:math/0205215},
  year   = {2007}
}

Comments

18 pages