OFFSET
0,3
LINKS
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 581
FORMULA
E.g.f.: (-1+3*x)/(-1+3*x+x^2)
D-finite Recurrence: {a(1)=0, a(0)=1, (-2-n^2-3*n)*a(n)+(-6-3*n)*a(n+1)+a(n+2)=0}
Sum(1/13*(-3+11*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+3*_Z+_Z^2))*n!
a(n)=n!*A006190(n-1). - R. J. Mathar, Jun 03 2022
MAPLE
spec := [S, {S=Sequence(Prod(Z, Z, Sequence(Union(Z, Z, Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
STATUS
approved