A116786 Number of permutations of length n which avoid the patterns 2314, 2431, 4123.

1, 2, 6, 21, 72, 228, 670, 1864, 5000, 13099, 33789, 86239, 218432, 550107, 1379348, 3446817, 8590103, 21362792, 53037845, 131501095, 325690131, 805941635, 1992965105, 4925514322, 12167639830, 30047049122, 74176872249, 183075826494

Offset

1,2

Links

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

David Callan and Toufik Mansour, Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns, arXiv:1705.00933 (2017), Table 2 No 43.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (9,-34,71,-90,70,-31,6)

Formula

G.f.: -x*(6*x^6-22*x^5+35*x^4-36*x^3+22*x^2-7*x+1)/((2*x-1)*(3*x^3-5*x^2+4*x-1)*(x-1)^3).

Crossrefs

Sequence in context: A116750 A116791 A116775 * A116748 A116812 A116830

Adjacent sequences: A116783 A116784 A116785 * A116787 A116788 A116789

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved