A116776 Number of permutations of length n which avoid the patterns 2134, 3142, 3421.

1, 2, 6, 21, 73, 239, 734, 2133, 5924, 15859, 41202, 104433, 259312, 632815, 1521646, 3612653, 8482796, 19726315, 45481962, 104071145, 236519400, 534249447, 1200095206, 2682257381, 5967445988, 13220446179, 29175578594, 64156073953

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 [math.CO] (2017), Table 2 No 82.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (10,-41,88,-104,64,-16).

Formula

G.f.: A(x) = {(x^6-14x^5+37x^4-45x^3+27x^2-8x+1)x}/{(2x-1)^4(x-1)^2}.

Crossrefs

Sequence in context: A116757 A116839 A294800 * A116754 A294801 A116768

Adjacent sequences: A116773 A116774 A116775 * A116777 A116778 A116779

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved