A116805 Number of permutations of length n which avoid the patterns 2134, 3214, 4123.

1, 2, 6, 21, 74, 256, 876, 2987, 10182, 34726, 118492, 404441, 1380670, 4713644, 16093028, 54944551, 187591798, 640477650, 2186726460, 7465949877, 25490345790, 87029482456, 297137237124, 1014489982275, 3463685453334

Offset

1,2

Links

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

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 135.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (8,-24,36,-29,12,-2).

Formula

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

Crossrefs

Sequence in context: A294768 A116793 A294805 * A116790 A116817 A116764

Adjacent sequences: A116802 A116803 A116804 * A116806 A116807 A116808

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved