Journal of Integer Sequences, Vol. 26 (2023), Article 23.4.2

Pattern-Avoidance and Fuss-Catalan Numbers


Per Alexandersson
Department of Mathematics
Stockholm University
S-106 91 Stockholm
Sweden

Frether Getachew Kebede
Department of Mathematics
Addis Ababa University
1176 Addis Ababa
Ethiopia

Samuel Asefa Fufa
Department of Mathematics
Addis Ababa University
1176 Addis Ababa
Ethiopia

Dun Qiu
Center for Combinatorics, LPMC
Nankai University
Tianjin 300071
P. R. China

Abstract:

We study a subset of permutations where entries are restricted to having the same remainder as the index, modulo some integer k ≥ 2. We show that by also imposing the classical 132- or 213-avoidance restriction on the permutations, we recover the Fuss–Catalan numbers and some special cases of the Raney numbers. Surprisingly, an analogous statement also holds when we impose the mod k restriction on a Catalan family of subexcedant functions. Finally, we completely enumerate all combinations of mod-k-alternating permutations that avoid two patterns of length 3. This is analogous to the systematic study by Simion and Schmidt, of permutations avoiding two patterns of length 3.


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(Concerned with sequences A000027 A000045 A000079 A000124 A047749 A079508 A335109 A354208 A355089 A355262.)


Received May 24 2022; revised versions received January 23 2023; January 24 2023; February 25 2023; April 6 2023. Published in Journal of Integer Sequences, April 7 2023.


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