A052665 a(0)=0, for n >= 1, a(n) = (2^(n-1)-1)*n!.

0, 0, 2, 18, 168, 1800, 22320, 317520, 5120640, 92534400, 1854316800, 40834886400, 980516275200, 25499650176000, 714077383219200, 21423629170944000, 685577056260096000, 23309975600271360000

Offset

0,3

Links

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

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 612

Formula

E.g.f.: x^2/((1-x)*(1-2*x)).

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

a(n) = n!*A0000225(n-1). - R. J. Mathar, Jun 03 2022

Maple

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

Mathematica

Join[{0}, Table[(2^(n-1)-1)n!, {n, 20}]] (* or *) With[{nn=20}, CoefficientList[ Series[x^2/((1-x)(1-2x)), {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Aug 29 2021 *)

Crossrefs

Sequence in context: A037623 A052865 A052883 * A259880 A364524 A092473

Adjacent sequences: A052662 A052663 A052664 * A052666 A052667 A052668

Keyword

easy,nonn

Author

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

Status

approved