A116759 Number of permutations of length n which avoid the patterns 2134, 3421, 4123.

1, 2, 6, 21, 71, 209, 533, 1205, 2473, 4696, 8372, 14169, 22959, 35855, 54251, 79865, 114785, 161518, 223042, 302861, 405063, 534381, 696257, 896909, 1143401, 1443716, 1806832, 2242801, 2762831, 3379371

Offset

1,2

Links

Table of n, a(n) for n=1..30.

D. Callan, T. Mansour, Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns, arXiv:1705.00933 (2017), Table 2 No 22.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (7,-21,35,-35,21,-7,1)

Formula

G.f.: A(x) = -{(x^6-8x^5+15x^4-14x^3+13x^2-5x+1)x}/{(x-1)^7}

(n^6 + 5n^5 - 55n^4 + 195n^3 - 186n^2 + 40n + 240)/240. - Franklin T. Adams-Watters, Sep 16 2006

Crossrefs

Sequence in context: A116766 A116825 A116767 * A116835 A294725 A116755

Adjacent sequences: A116756 A116757 A116758 * A116760 A116761 A116762

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved