A116817 Number of permutations of length n which avoid the patterns 2341, 3241, 4132.

1, 2, 6, 21, 74, 257, 881, 2995, 10132, 34182, 115143, 387538, 1303745, 4384933, 14746009, 49585430, 166730986, 560620697, 1885023706, 6338138505, 21311063589, 71655198707, 240929422288, 810087129234, 2723789200907

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 137, 138 and 139.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (6,-10,3,3,-1).

Formula

G.f.: A(x) = -{x(-1+4x+x^4-2x^3-4x^2)}/{(x^4-2x^3-5x^2+5x-1)(x-1)}

Crossrefs

Sequence in context: A294805 A116805 A116790 * A116764 A294769 A116738

Adjacent sequences: A116814 A116815 A116816 * A116818 A116819 A116820

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved