A116760 Number of permutations of length n which avoid the patterns 2341, 3214, 4213; or avoid the patterns 1324, 2341, 3214.

1, 2, 6, 21, 73, 245, 795, 2508, 7732, 23393, 69687, 204939, 596215, 1718714, 4915914, 13966077, 39445669, 110840321, 310052883, 863847240, 2398229056, 6636793817, 18313798131, 50404632471, 138400646383, 379203110390

Offset

1,2

Links

Table of n, a(n) for n=1..26.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (8,-23,28,-13,2)

Formula

G.f.: A(x) = {(9x^3-13x^2+6x-1)x}/{(x^2-3x+1)^2(2x-1)}

Crossrefs

Sequence in context: A116802 A294697 A116826 * A116828 A294764 A116837

Adjacent sequences: A116757 A116758 A116759 * A116761 A116762 A116763

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved