A052615 E.g.f. x^3*(1+2x-2x^2)/(1-x).

0, 0, 0, 6, 72, 120, 720, 5040, 40320, 362880, 3628800, 39916800, 479001600, 6227020800, 87178291200, 1307674368000, 20922789888000, 355687428096000, 6402373705728000, 121645100408832000, 2432902008176640000

Offset

0,4

Links

Table of n, a(n) for n=0..20.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 560

Formula

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

Recurrence: {a(1)=0, a(0)=0, a(2)=0, (-1-n)*a(n)+a(n+1)=0, a(3)=6, a(4)=72, a(5)=120}

n!, n>5.

Maple

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

Crossrefs

Sequence in context: A167813 A242232 A259139 * A340506 A338535 A250071

Adjacent sequences: A052612 A052613 A052614 * A052616 A052617 A052618

Keyword

easy,nonn

Author

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

Status

approved