A052793 A simple grammar.

0, 0, 0, 0, 0, 0, 720, 5040, 23520, 90720, 312480, 997920, 3017520, 8751600, 24552528, 67026960, 178825920, 467812800, 1203094080, 3048024384, 7620293520

Offset

0,7

Links

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

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 750

Formula

E.g.f.: x^4*exp(x)^2-2*x^4*exp(x)+x^4

D-finite Recurrence: {a(1)=0, a(2)=0, a(4)=0, a(3)=0, a(5)=0, a(6)=720, (2*n^2+6*n+4)*a(n)+(18-3*n^2+3*n)*a(n+1)+(n^2-5*n+6)*a(n+2)=0}

Maple

spec := [S, {B=Set(Z, 1 <= card), S=Prod(Z, Z, Z, Z, B, B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);

Crossrefs

Sequence in context: A187290 A218487 A053625 * A179728 A052799 A229569

Adjacent sequences: A052790 A052791 A052792 * A052794 A052795 A052796

Keyword

easy,nonn

Author

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

Status

approved