A116745 Number of permutations of length n which avoid the patterns 2134, 3214, 4312.

1, 2, 6, 21, 74, 246, 763, 2227, 6191, 16567, 43026, 109110, 271384, 664236, 1603813, 3827381, 9040909, 21164253, 49147156, 113305760, 259515246, 590863722, 1337972351, 3014643351, 6761203099, 15099476851, 33587965958, 74440483642

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 116.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (13,-74,242,-501,681,-608,344,-112,16).

Formula

G.f.: A(x) = -{x(15x^8-89x^7+211x^6-293x^5+262x^4-151x^3+54x^2-11x+1)}/{(2x-1)^4(x-1)^5}

Crossrefs

Sequence in context: A148489 A116771 A294765 * A116831 A294698 A294766

Adjacent sequences: A116742 A116743 A116744 * A116746 A116747 A116748

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved