A220874 Number of permutations of [n+1] avoiding 2413, 3142, 1324, 4231.

1, 2, 6, 20, 64, 194, 562, 1570, 4258, 11266, 29186, 74242, 185858, 458754, 1118210, 2695170, 6430722, 15204354, 35651586, 82968578, 191758338, 440401922, 1005584386, 2283798530, 5161091074, 11609833474, 26004684802, 58015612930, 128949682178

Offset

0,2

Links

Table of n, a(n) for n=0..28.

Andrei Asinowski and Toufik Mansour, Separable d-Permutations and Guillotine Partitions, arXiv:0803.3414 [math.CO], 2008.

Andrei Asinowski and Toufik Mansour, Separable d-Permutations and Guillotine Partitions, Annals of Combinatorics 14 (1) pp.17-43 Springer, 2010.

Index entries for linear recurrences with constant coefficients, signature (9,-32,56,-48,16).

Formula

Andrei Asinowski and Toufik Mansour give a g.f.

G.f. -(-7*x+20*x^2-26*x^3+12*x^4+2*x^5+1)/((x-1)*(2*x-1)^4). - R. J. Mathar, Jan 04 2013

a(n) = 2+(n-1)*(n^2+n+42)*2^(n-4)/3 for n>0. - R. J. Mathar, Jan 30 2013 (see Maple section).

Maple

A220874 := proc(n)
    if n = 0 then
        1;
    else
        2+(n-1)*(n^2+n+42)*2^(n-4)/3 ;
    end if;
end proc: # R. J. Mathar, Jan 30 2013

Mathematica

a[0] = 1; a[n_] := 2 + (n - 1)*(n^2 + n + 42)*2^(n - 4)/3;
Table[a[n], {n, 0, 28}] (* Jean-François Alcover, Dec 01 2017, after R. J. Mathar *)

Crossrefs

Sequence in context: A193235 A199102 A053730 * A273902 A181301 A302612

Adjacent sequences: A220871 A220872 A220873 * A220875 A220876 A220877

Keyword

nonn,easy

Author

N. J. A. Sloane, Dec 27 2012

Status

approved