Callan, David, Mansour, Toufik, Shattuck, Mark (2017) Twelve subsets of permutations enumerated as maximally clustered permutations Annales Mathematicae et Informaticae. 47. pp. 41-74. ISSN 1787-5021 (Print), 1787-6117 (Online)
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Absztrakt (kivonat)
The problem of avoiding a single pattern or a pair of patterns of length four by permutations has been well studied. Less is known about the avoidance of three 4-letter patterns. In this paper, we show that the number of members of S avoiding any one of twelve triples of 4-letter patterns is given by sequence A129775 in OEIS, which is known to count maximally clustered permutations. Numerical evidence confirms that there are no other (non-trivial) triples of 4letter patterns giving rise to this sequence and hence one obtains the largest (4, 4, 4)-Wilf-equivalence class for permutations. We make use of a variety of methods in proving our result, including recurrences, the kernel method, direct counting, and bijections.
Mű típusa: | Folyóiratcikk | ||||||||||||||||
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Kulcsszavak: | pattern avoidance; Wilf-equivalence; kernel method; maximally clustered permutations | ||||||||||||||||
Nyelv: | angol | ||||||||||||||||
Kötetszám: | 47. | ||||||||||||||||
ISSN: | 1787-5021 (Print), 1787-6117 (Online) | ||||||||||||||||
Felhasználó: | Tibor Gál | ||||||||||||||||
Dátum: | 12 Már 2019 16:53 | ||||||||||||||||
Utolsó módosítás: | 12 Már 2019 16:53 | ||||||||||||||||
URI: | http://publikacio.uni-eszterhazy.hu/id/eprint/3285 |
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