A116819 - OEIS

A116819

Number of permutations of length n which avoid the patterns 2431, 4123, 4231.

1, 2, 6, 21, 76, 274, 978, 3463, 12201, 42869, 150415, 527426, 1848905, 6480722, 22715293, 79617891, 279063942, 978133274, 3428414441, 12016810218, 42119714480, 147632440224, 517461749617, 1813738775801, 6357278456431

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..25.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (7,-16,14,-3).

FORMULA

G.f.: A(x) = -{(3x^3-8x^2+5x-1)x}/{3x^4-14x^3+16x^2-7x+1}

MATHEMATICA

LinearRecurrence[{7, -16, 14, -3}, {1, 2, 6, 21}, 30] (* Harvey P. Dale, Mar 31 2023 *)

CROSSREFS

Sequence in context: A294772 A294818 A116809 * A294819 A294820 A116782

Adjacent sequences: A116816 A116817 A116818 * A116820 A116821 A116822

KEYWORD

nonn,easy

AUTHOR

Lara Pudwell, Feb 26 2006

STATUS

approved