A116758 Number of permutations of length n which avoid the patterns 1234, 1432, 2341.

1, 2, 6, 21, 72, 232, 717, 2157, 6370, 18557, 53490, 152868, 433781, 1223511, 3433182, 9590277, 26683932, 73986112, 204501885, 563677377, 1549776250, 4251231533, 11637412806, 31795910076, 86721532517, 236147429547

Offset

1,2

Links

Table of n, a(n) for n=1..26.

D. Callan, T. Mansour, Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns, arXiv:1705.00933 (2017), Table 2 No 52.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (8,-24,34,-24,8,-1)

Formula

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

Crossrefs

Sequence in context: A116810 A294703 A116800 * A116838 A116836 A116796

Adjacent sequences: A116755 A116756 A116757 * A116759 A116760 A116761

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved