A116751 Number of permutations of length n which avoid the patterns 2314, 2431, 3124.

1, 2, 6, 21, 75, 265, 929, 3249, 11362, 39746, 139060, 486549, 1702349, 5956172, 20839367, 72912441, 255104933, 892557394, 3122866871, 10926241348, 38228574601, 133753581322, 467975086412, 1637344431204, 5728716901208

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 (6,-12,13,-6,1)

Formula

G.f.: A(x) = -{x(x-1)^4}/{x^5-6x^4+13x^3-12x^2+6x-1}

Crossrefs

Sequence in context: A116820 A369626 A294815 * A116823 A289597 A116743

Adjacent sequences: A116748 A116749 A116750 * A116752 A116753 A116754

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved