A116810 Number of permutations of length n which avoid the patterns 2134, 3241, 4132.

1, 2, 6, 21, 72, 230, 692, 2004, 5683, 15948, 44523, 123924, 344113, 953353, 2635064, 7266192, 19990484, 54876361, 150331490, 411034895, 1121843295, 3056805471, 8316456845, 22593934835, 61301610481, 166118362404, 449639670226

Offset

1,2

Links

Table of n, a(n) for n=1..27.

D. Callan, T. Mansour, Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns, arXiv:1705.00933 (2017), Table 2 No 48.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (12,-62,182,-337,412,-337,182,-62,12,-1).

Formula

G.f.: A(x) = -{(x^9-11x^8+47x^7=109x^6+162x^5-165x^4+109x^3-44x^2+10x-1)x}/{(x^2-3x+1)^2(x-1)^6}

Crossrefs

Sequence in context: A116812 A116830 A116747 * A294703 A116800 A116758

Adjacent sequences: A116807 A116808 A116809 * A116811 A116812 A116813

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved