A116779 Number of permutations of length n which avoid the patterns 2143, 2341, 3214.

1, 2, 6, 21, 72, 237, 761, 2415, 7626, 24034, 75689, 238298, 750179, 2361533, 7433917, 23401274, 73664906, 231889749, 729965584, 2297858029, 7233425149, 22770092131, 71677951146, 225634953382, 710276052265, 2235877300106

Offset

1,2

Links

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

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (6,-12,11,-5,1).

Formula

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

Crossrefs

Sequence in context: A116838 A116836 A116796 * A116737 A360153 A294759

Adjacent sequences: A116776 A116777 A116778 * A116780 A116781 A116782

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved