A052596 E.g.f. (1+x^4-x^5)/(1-x).

1, 1, 2, 6, 48, 120, 720, 5040, 40320, 362880, 3628800, 39916800, 479001600, 6227020800, 87178291200, 1307674368000, 20922789888000, 355687428096000, 6402373705728000, 121645100408832000, 2432902008176640000

Offset

0,3

Links

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

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 541

Formula

E.g.f.: (-1-x^4+x^5)/(-1+x)

Recurrence: {a(1)=1, a(0)=1, (-1-n)*a(n)+a(n+1)=0, a(3)=6, a(2)=2, a(5)=120, a(4)=48}

n!, n>4.

Maple

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

Mathematica

With[{nn=30}, CoefficientList[Series[(1+x^4-x^5)/(1-x), {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Dec 25 2011 *)

Crossrefs

Sequence in context: A274702 A072444 A334807 * A344676 A098710 A337907

Adjacent sequences: A052593 A052594 A052595 * A052597 A052598 A052599

Keyword

easy,nonn

Author

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

Status

approved