A116770 Number of permutations of length n which avoid the patterns 1243, 1342, 4312.

1, 2, 6, 21, 73, 234, 691, 1910, 5019, 12690, 31147, 74694, 175843, 407810, 934179, 2117958, 4759915, 10617234, 23527867, 51839462, 113639955, 247988802, 538968691, 1167065766, 2518680283, 5419041554, 11626611531, 24880612230

Offset

1,2

Links

Table of n, a(n) for n=1..28.

D. Callan, T. Mansour, Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns, arXiv:1705.00933 (2017), Table 2 No 68.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (9,-33,63,-66,36,-8).

Formula

G.f.: A(x) = {x(3x^6-12x^5+22x^4-30x^3+21x^2-7x+1)}/{(2x-1)^3(x-1)^3}

a(n)=2^n*(-99/16+29n/32+3n^2/32)+n^2+4n+6, n>1. [From R. J. Mathar, Aug 05 2008]

Crossrefs

Sequence in context: A116789 A116783 A116739 * A294796 A116753 A294762

Adjacent sequences: A116767 A116768 A116769 * A116771 A116772 A116773

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved