The enumeration of maximally clustered permutations
Abstract
The maximally clustered permutations are characterized by avoiding the classical permutation patterns 3421, 4312, and 4321. This class contains the freely-braided permutations and the fully-commutative permutations. In this work, we show that the generating functions for certain fully-commutative pattern classes can be transformed to give generating functions for the corresponding freely-braided and maximally clustered pattern classes. Moreover, this transformation of generating functions is rational. As a result, we obtain enumerative formulas for the pattern classes mentioned above as well as the corresponding hexagon-avoiding pattern classes where the hexagon-avoiding permutations are characterized by avoiding 46718235, 46781235, 56718234, and 56781234.
Keywords
Cite
@article{arxiv.0704.3469,
title = {The enumeration of maximally clustered permutations},
author = {Hugh Denoncourt and Brant C. Jones},
journal= {arXiv preprint arXiv:0704.3469},
year = {2008}
}