A052793 - OEIS

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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

(list; graph; refs; listen; history; text; internal format)

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