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URL: https://oeis.org/A116763

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A116763

Number of permutations of length n which avoid the patterns 2134, 3241, 3421.

0

1, 2, 6, 21, 75, 255, 813, 2443, 6985, 19175, 50917, 131555, 332257, 823263, 2007005, 4825051, 11460569, 26935255, 62717909, 144834515, 332005329, 756023247, 1711275981, 3852468171, 8629780425, 19243466695, 42731569093, 94522834883

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..28.

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 145.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (10,-41,88,-104,64,-16)

FORMULA

G.f.: A(x) = {x(2x^6-18x^5+39x^4-45x^3+27x^2-8x+1)}/{(x-1)^2(2x-1)^4}

CROSSREFS

Sequence in context: A150187 A116818 A294770 * A116840 A116841 A116814

Adjacent sequences: A116760 A116761 A116762 * A116764 A116765 A116766

KEYWORD

nonn,easy

AUTHOR

Lara Pudwell, Feb 26 2006

STATUS

approved