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A116744

Number of permutations of length n which avoid the patterns 1243, 1432, 4213.

1, 2, 6, 21, 73, 242, 772, 2409, 7439, 22872, 70204, 215345, 660375, 2024866, 6208416, 19035179, 58361985, 178937794, 548622648, 1682074579, 5157232471, 15812048862, 48479661510, 148638395025, 455724560391, 1397249174878

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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 100 and 101.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (8,-26,47,-52,35,-13,2).

FORMULA

G.f.: A(x) = -{(x^2-x+1)(2x^4-7x^3+10x^2-5x+1)x}/{(2x^4-7x^3+8x^2-5x+1)(x-1)^3}

MATHEMATICA

LinearRecurrence[{8, -26, 47, -52, 35, -13, 2}, {1, 2, 6, 21, 73, 242, 772}, 30] (* Harvey P. Dale, Sep 07 2019 *)

CROSSREFS

Sequence in context: A116822 A116797 A294804 * A165521 A294696 A116784

Adjacent sequences: A116741 A116742 A116743 * A116745 A116746 A116747

KEYWORD

nonn,easy

AUTHOR

Lara Pudwell, Feb 26 2006

STATUS

approved

URL: https://oeis.org/A116744

⇱ A116744 - OEIS