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A116814

Number of permutations of length n which avoid the patterns 3124, 3421, 4231.

1, 2, 6, 21, 75, 258, 845, 2649, 8019, 23630, 68216, 193861, 544312, 1514024, 4180488, 11476203, 31358553, 85367436, 231691655, 627259131, 1694678721, 4570645292, 12309288446, 33108960151, 88958761210, 238792953938

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..26.

D. Callan, T. Mansour, Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns, arXiv:1705.00933 [math.CO] (2017), Table 2 No 148.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (13,-72,222,-418,496,-369,165,-40,4).

FORMULA

G.f.: -(4x^8 -35x^7 +114x^6 -197x^5 +208x^4 -135x^3 +52x^2 -11x+1)*x/((x^2-3x+1)^2 (x-1)^3 (2x-1)^2).

MATHEMATICA

LinearRecurrence[{13, -72, 222, -418, 496, -369, 165, -40, 4}, {1, 2, 6, 21, 75, 258, 845, 2649, 8019}, 30] (* Harvey P. Dale, Aug 17 2025 *)

CROSSREFS

Sequence in context: A116763 A116840 A116841 * A294806 A294807 A294771

Adjacent sequences: A116811 A116812 A116813 * A116815 A116816 A116817

KEYWORD

nonn,easy

AUTHOR

Lara Pudwell, Feb 26 2006

STATUS

approved

URL: https://oeis.org/A116814

⇱ A116814 - OEIS