OFFSET
0,4
LINKS
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 571
FORMULA
E.g.f.: -(-1+x)^2/(-1+2*x-x^2+x^3)
Recurrence: {a(1)=0, a(0)=1, a(2)=0, (-11*n-6-n^3-6*n^2)*a(n) +(n^2+5*n+6)*a(n+1) +(-2*n-6)*a(n+2) +a(n+3)=0}
Sum(-1/23*(2-11*_alpha+6*_alpha^2)*_alpha^(-1-n), _alpha=RootOf(-1+2*_Z-_Z^2+_Z^3))*n!
a(n) = (-1)^n*n!*A099529(n). - R. J. Mathar, Jun 03 2022
MAPLE
spec := [S, {S=Sequence(Prod(Z, Z, Z, Sequence(Z), Sequence(Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
MATHEMATICA
With[{nn=20}, CoefficientList[Series[(1-x)^2/(1-2x+x^2-x^3), {x, 0, nn}], x]Range[0, nn]!] (* Harvey P. Dale, May 22 2012 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
STATUS
approved