A052663 E.g.f. x^4*(1+x-x^2)/(1-x).

0, 0, 0, 0, 24, 240, 720, 5040, 40320, 362880, 3628800, 39916800, 479001600, 6227020800, 87178291200, 1307674368000, 20922789888000, 355687428096000, 6402373705728000, 121645100408832000, 2432902008176640000

Offset

0,5

Links

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

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 610

Formula

E.g.f.: x^4*(-x+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)=0, a(4)=24, a(6)=720, a(5)=240}

n! for n >= 4.

Maple

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

Crossrefs

Sequence in context: A003245 A006863 A335128 * A192491 A167548 A192849

Adjacent sequences: A052660 A052661 A052662 * A052664 A052665 A052666

Keyword

easy,nonn

Author

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

Status

approved