A116783 Number of permutations of length n which avoid the patterns 1234, 2431, 4231.

1, 2, 6, 21, 73, 232, 654, 1639, 3705, 7678, 14798, 26841, 46257, 76324, 121318, 186699, 279313, 407610, 581878, 814493, 1120185, 1516320, 2023198, 2664367, 3466953, 4462006, 5684862, 7175521, 8979041, 11145948

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 66.

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(3x^6+x^5+17x^4-14x^3+13x^2-5x+1)}/{(x-1)^7}

a(n) = (4n^6 - 45n^5 + 250n^4 - 735n^3 + 1276n^2 - 1110n + 540)/180. - Franklin T. Adams-Watters, Sep 16 2006

Crossrefs

Sequence in context: A116829 A116824 A116789 * A116739 A116770 A294796

Adjacent sequences: A116780 A116781 A116782 * A116784 A116785 A116786

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved