A116750 Number of permutations of length n which avoid the patterns 1234, 2341, 4312.

1, 2, 6, 21, 72, 216, 555, 1252, 2549, 4787, 8428, 14079, 22518, 34722, 51897, 75510, 107323, 149429, 204290, 274777, 364212, 476412, 615735, 787128, 996177, 1249159, 1553096, 1915811, 2345986, 2853222

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 40.

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(x^8-5x^7+5x^6+8x^5-16x^4+14x^3-13x^2+5x-1)}/{(x-1)^7}

For n >= 3, a(n) = (n^6 + 15n^5 - 80n^4 - 105n^3 + 1519n^2 - 2430n + 720)/360. - Franklin T. Adams-Watters, Sep 16 2006

Crossrefs

Sequence in context: A148486 A294753 A294754 * A116791 A116775 A116786

Adjacent sequences: A116747 A116748 A116749 * A116751 A116752 A116753

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved