English

Increasing Consecutive Patterns in Words

Combinatorics 2018-05-23 v2

Abstract

We show how to enumerate words in 1m1nmn1^{m_1} \dots n^{m_n} that avoid the increasing consecutive pattern 12r12 \dots r for any r2r \geq 2. Our approach yields an O(ns+1)O(n^{s+1}) algorithm to enumerate words in 1sns1^s \dots n^s, avoiding the consecutive pattern 1r1\dots r, for any ss, and any rr. This enables us to supply many more terms to quite a few OEIS sequences, and create new ones. We also treat the more general case of counting words with a specified number of the pattern of interest (the avoiding case corresponding to zero appearances). This article is accompanied by three Maple packages implementing our algorithms.

Keywords

Cite

@article{arxiv.1805.06077,
  title  = {Increasing Consecutive Patterns in Words},
  author = {Mingjia Yang and Doron Zeilberger},
  journal= {arXiv preprint arXiv:1805.06077},
  year   = {2018}
}

Comments

After the first version of the current paper was posted, Justin Troyka pointed out that our Theorem 1 is not new and it goes back to Ira Gessel. Thus we have this second version