OFFSET
0,3
LINKS
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 552
FORMULA
E.g.f.: (-1+x^3)/(-1+x^2+x^3)
Recurrence: {a(1)=0, a(0)=1, a(3)=0, a(2)=2, (-11*n-6-n^3-6*n^2)*a(n) +(-n^2-5*n-6)*a(n+1) +a(n+3)=0}
Sum(-1/23*(6*_alpha^2+2*_alpha-9)*_alpha^(-1-n), _alpha=RootOf(_Z^3+_Z^2-1))*n!
MAPLE
spec := [S, {S=Sequence(Prod(Z, Z, Sequence(Prod(Z, Z, Z))))}, labeled]: [seq(combstruct[count](spec, size=n), n=0..20)];
MATHEMATICA
With[{nn=20}, CoefficientList[Series[(1-x^3)/(1-x^2-x^3), {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Jan 04 2012 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
STATUS
approved