Standard young tableaux of height 4 and 5
European Journal of Combinatorics
Symmetric functions and P-Recursiveness
Journal of Combinatorial Theory Series A
Discrete Mathematics
Classification of forbidden subsequences of length 4
European Journal of Combinatorics
Exact enumeration of 1342-avoiding permutations: a close link with labeled trees and planar maps
Journal of Combinatorial Theory Series A
Some permutations with forbidden subsequences and their inversion number
Discrete Mathematics
Permutations with Restricted Patterns and Dyck Paths
Advances in Applied Mathematics
A New Class of Wilf-Equivalent Permutations
Journal of Algebraic Combinatorics: An International Journal
Simple permutations and algebraic generating functions
Journal of Combinatorial Theory Series A
On bijections for pattern-avoiding permutations
Journal of Combinatorial Theory Series A
Counting permutations with no long monotone subsequence via generating trees and the kernel method
Journal of Algebraic Combinatorics: An International Journal
Modified growth diagrams, permutation pivots, and the BWX map φ
Journal of Combinatorial Theory Series A
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In a recent paper, Backelin, West and Xin describe a map 驴* that recursively replaces all occurrences of the pattern k... 21 in a permutation 驴 by occurrences of the pattern (k驴1)... 21 k. The resulting permutation 驴*(驴) contains no decreasing subsequence of length k. We prove that, rather unexpectedly, the map 驴* commutes with taking the inverse of a permutation.In the BWX paper, the definition of 驴* is actually extended to full rook placements on a Ferrers board (the permutations correspond to square boards), and the construction of the map 驴* is the key step in proving the following result. Let T be a set of patterns starting with the prefix 12... k. Let T驴 be the set of patterns obtained by replacing this prefix by k... 21 in every pattern of T. Then for all n, the number of permutations of the symmetric group $${\cal S}$$ n that avoid T equals the number of permutations of $${\cal S}$$ n that avoid T驴.Our commutation result, generalized to Ferrers boards, implies that the number of involutions of $${\cal S}$$ n that avoid T is equal to the number of involutions of $${\cal S}$$ n avoiding T驴, as recently conjectured by Jaggard.