0000000000007175
AUTHOR
Armen Petrossian
Equivalence classes of permutations modulo excedances
International audience
Pattern avoiding permutations modulo pure descent
International audience
Equivalence classes of permutations modulo descents and left-to-right maxima
Abstract In a recent paper [2], the authors provide enumerating results for equivalence classes of permutations modulo excedances. In this paper we investigate two other equivalence relations based on descents and left-to-right maxima. Enumerating results are presented for permutations, involutions, derangements, cycles and permutations avoiding one pattern of length three.
Enumeration of Łukasiewicz paths modulo some patterns
Abstract For any pattern α of length at most two, we enumerate equivalence classes of Łukasiewicz paths of length n ≥ 0 where two paths are equivalent whenever the occurrence positions of α are identical on these paths. As a byproduct, we give a constructive bijection between Motzkin paths and some equivalence classes of Łukasiewicz paths.
Dyck paths with a first return decomposition constrained by height
International audience; We study the enumeration of Dyck paths having a first return decomposition with special properties based on a height constraint. We exhibit new restricted sets of Dyck paths counted by the Motzkin numbers, and we give a constructive bijection between these objects and Motzkin paths. As a byproduct, we provide a generating function for the number of Motzkin paths of height k with a flat (resp. with no flats) at the maximal height. (C) 2018 Elsevier B.V. All rights reserved.KeywordsKeyWords Plus:STATISTICS; STRINGS
Motzkin Paths With a Restricted First Return Decomposition
International audience
Equivalence classes of Dyck paths modulo some statistics
International audience; We investigate new equivalence relations on the set $\mathcal{D}_n$ of Dyck paths relatively to the three statistics of double rises, peaks and valleys. Two Dyck paths ar $r$-equivalent (resp. $p$-equivalent and $v$-equivalent) whenever the positions of their double rises (res. peaks and valleys) are the same. Then, we provide generating functions for the numbers of $r$-, $p$- and $v$-equivalence classes of $\mathcal{D}_n$.
Forests and pattern-avoiding permutations modulo pure descents
Abstract We investigate an equivalence relation on permutations based on the pure descent statistic. Generating functions are given for the number of equivalence classes for the set of all permutations, and the sets of permutations avoiding exactly one pattern of length three. As a byproduct, we exhibit a permutation set in one-to-one correspondence with forests of ordered binary trees, which provides a new combinatorial class enumerated by the single-source directed animals on the square lattice. Furthermore, bivariate generating functions for these sets are given according to various statistics.
Permutations avoiding generalized patterns modulo left-to-right maxima
International audience