For each positive integer k, we consider five well-studied posets defined on the set of Dyck
paths of semilength k. We prove that uniquely sorted permutations avoiding various patterns …

We have made a systematic numerical study of the 16 Wilf classes of length-5 classical
pattern-avoiding permutations from their generating function coefficients. We have extended …

Wilf classification of triples of 4-letter patterns II Page 1 Discrete Mathematics and Theoretical
Computer Science DMTCS vol. 19:1, 2017, #6 Wilf classification of triples of 4-letter patterns II …

1. Introduction Page 1 Journal of Combinatorics and Number Theory Volume 8, Number 3, pp.
257–283 WILF CLASSIFICATION OF SUBSETS OF EIGHT AND NINE FOUR-LETTER …

Let π= π1π2··· πn∈ Sn and τ= τ1τ2··· τk∈ Sk be two permutations. We say that π contains τ
if there exists a subsequence 1≤ i1< i2<···< ik≤ n such that πi1 πi2··· πik is order …

We introduce an algorithm that produces conjectures regarding the structure of permutation
classes. These conjectures take the form of a disjoint cover of “rules”, each of which is …

Let Sn be the symmetric group of all permutations of n letters. We show that there are exactly
1100 distinct Wilf classes for the permutations avoiding four patterns of length 4. Moreover …

1. Introduction Page 1 Journal of Combinatorics and Number Theory Volume 9, Number 3,
pp. 169–213 ISSN 1942-5600 c Nova Science Publishers, Inc. WILF CLASSIFICATION OF …

This paper is one of a series whose goal is to enumerate the avoiders, in the sense of
classical pattern avoidance, for each triple of 4-letter patterns. There are 317 symmetry …

We develop a new, powerful method for counting elements in a {\em multiset.} As a first
application, we use this algorithm to study the number of occurrences of patterns in a …