A116772 Number of permutations of length n which avoid the patterns 1234, 1243, 1432.

1, 2, 6, 21, 76, 278, 1021, 3756, 13827, 50916, 187512, 690593, 2543444, 9367525, 34500756, 127067006, 467990629, 1723620240, 6348133335, 23380322908, 86110274536, 317146150489, 1168056674504, 4301979997337, 15844292751908

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 206.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (7,-17,21,-13,2).

Formula

G.f.: A(x) = -{x(x-1)(x^4+3x^3-5x^2+4x-1)}/{-13x^4+21x^3-17x^2+7x-1+2x^5}

Crossrefs

Sequence in context: A116798 A279560 A116821 * A131792 A144904 A151287

Adjacent sequences: A116769 A116770 A116771 * A116773 A116774 A116775

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved