132-avoiding two-stack sortable permutations, Fibonacci numbers, and Pell numbers

Eric S. Egge, Toufik Mansour

Research output: Contribution to journalArticlepeer-review

Abstract

We describe the recursive structures of the set of two-stack sortable permutations which avoid 132 and the set of two-stack sortable permutations which contain 132 exactly once. Using these results and standard generating function techniques, we enumerate two-stack sortable permutations which avoid (or contain exactly once) 132 and which avoid (or contain exactly once) an arbitrary permutation τ. In most cases the number of such permutations is given by a simple formula involving Fibonacci or Pell numbers.

Original languageEnglish
Pages (from-to)72-83
Number of pages12
JournalDiscrete Applied Mathematics
Volume143
Issue number1-3
DOIs
StatePublished - 30 Sep 2004

Keywords

  • Fibonacci number
  • Forbidden subsequence
  • Pattern-avoiding permutation
  • Pell number
  • Restricted permutation
  • Two-stack sortable permutation

ASJC Scopus subject areas

  • Discrete Mathematics and Combinatorics
  • Applied Mathematics

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