A052626 (2^n+2)*n!.

3, 4, 12, 60, 432, 4080, 47520, 655200, 10402560, 186520320, 3723148800, 81829440000, 1962948556800, 51024208435200, 1428503479603200, 42852489039360000, 1371237803679744000, 46621373950255104000

Offset

0,1

Links

Table of n, a(n) for n=0..17.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 572

Formula

E.g.f.: -(-3+5*x)/(-1+2*x)/(-1+x)

Recurrence: {a(0)=3, a(1)=4, (2*n^2+6*n+4)*a(n)+(-6-3*n)*a(n+1)+a(n+2)=0}

(2^n+2)*n!

Maple

spec := [S, {S=Union(Sequence(Z), Sequence(Z), Sequence(Union(Z, Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);

Crossrefs

Sequence in context: A217477 A299809 A109771 * A336687 A298115 A122903

Adjacent sequences: A052623 A052624 A052625 * A052627 A052628 A052629

Keyword

easy,nonn

Author

encyclopedia(AT)pommard.inria.fr, Jan 25 2000

Status

approved