A116740 Number of permutations of length n which avoid the patterns 1243, 2341, 4132.

1, 2, 6, 21, 73, 239, 740, 2199, 6348, 17947, 49954, 137372, 374164, 1011303, 2716439, 7259970, 19324340, 51268390, 135658217, 358193704, 944162051, 2485297822, 6534794291, 17167312441, 45067797703, 118245785494

Offset

1,2

Links

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

David Callan and Toufik Mansour, Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns, arXiv:1705.00933 [math.CO] (2017), Table 2 No 87.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (12,-62,181,-329,386,-292,137,-36,4).

Formula

G.f.: -x*(6*x^8-36*x^7+91*x^6-149*x^5+160*x^4-108*x^3+44*x^2-10*x+1)/((2*x-1)^2*(x-1)^5*(x^2-3*x+1)).

Crossrefs

Sequence in context: A294801 A116768 A294694 * A294802 A116788 A294695

Adjacent sequences: A116737 A116738 A116739 * A116741 A116742 A116743

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved