A116792 Number of permutations of length n which avoid the patterns 1432, 2134, 2341.

1, 2, 6, 21, 71, 219, 635, 1776, 4853, 13068, 34862, 92438, 244118, 642947, 1690256, 4437947, 11642149, 30522573, 79988157, 209556918, 548894043, 1437513998, 3764362904, 9856889564, 25808724004, 67573730053, 176920646370

Offset

1,2

Links

Table of n, a(n) for n=1..27.

D. Callan, T. Mansour, Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns, arXiv:1705.00933 (2017), Table 2 No 32

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (7,-18,21,-12,7,-8,5,-1).

Formula

G.f.: A(x) = {(x^9-4x^8+3x^7+5x^6-9x^5+2x^4-6x^3+10x^2-5x+1)x}/{(x^3+x^2+x-1)(x-1)^3(x^2-3x+1)}

Crossrefs

Sequence in context: A294700 A294701 A116749 * A116761 A116807 A294702

Adjacent sequences: A116789 A116790 A116791 * A116793 A116794 A116795

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved