OFFSET
0,4
LINKS
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 527
FORMULA
E.g.f.: x*(-1+x)/(-1+x+x^2)
Recurrence: {a(1)=1, a(0)=0, a(2)=0, (-2-n^2-3*n)*a(n)+(-2-n)*a(n+1)+a(n+2)=0}
Sum(-1/5*(-3+4*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+_Z+_Z^2))*n!
a(n)=n!*A212804(n-1). - R. J. Mathar, Jun 03 2022
MAPLE
spec := [S, {S=Prod(Z, Sequence(Prod(Z, Z, Sequence(Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
MATHEMATICA
With[{nn=20}, CoefficientList[Series[x (1-x)/(1-x-x^2), {x, 0, nn}], x]Range[0, nn]!] (* Harvey P. Dale, Jul 24 2012 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
STATUS
approved