A052732 E.g.f.: (1-2x-sqrt(1-4*x))*x^2/2

0, 0, 0, 0, 24, 240, 3600, 70560, 1693440, 47900160, 1556755200, 57081024000, 2328905779200, 104589041356800, 5124863026483200, 272011960636416000, 15543540607795200000, 951264685197066240000, 62070020709108572160000

Offset

0,5

Comments

Apart from a(3) the same as A052733. - R. J. Mathar, Oct 16 2013

Links

Table of n, a(n) for n=0..18.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 688

Formula

Recurrence: a(1)=0; a(2)=0; a(3)=0; a(4)=24; (-4*n^2+6*n+10)*a(n)+(n-1)*a(n+1)=0 ; a(5)=240;

a(n) = n!*A000108(n-3), n>3. - R. J. Mathar, Oct 16 2013

Maple

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

Crossrefs

Sequence in context: A000536 A151720 A052652 * A267060 A086603 A304835

Adjacent sequences: A052729 A052730 A052731 * A052733 A052734 A052735

Keyword

easy,nonn

Author

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

Status

approved