OFFSET
0,3
LINKS
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 533
FORMULA
E.g.f.: -(-1+x)/(1-x-x^3+x^4-x^2)
Recurrence: {a(1)=0, a(0)=1, a(2)=2, a(3)=12, (n^4+35*n^2+50*n+24+10*n^3)*a(n) +(-n^3-9*n^2-26*n-24)*a(n+1) +(-n^2-7*n-12)*a(n+2) +(-n-4)*a(n+3) +a(n+4)=0}
Sum(-1/39*(-2-11*_alpha+4*_alpha^2+_alpha^3)*_alpha^(-1-n), _alpha=RootOf(1-_Z-_Z^3+_Z^4-_Z^2))*n!
a(n) = n!*A052527(n). - R. J. Mathar
MAPLE
spec := [S, {S=Sequence(Prod(Z, Z, Union(Z, Sequence(Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
MATHEMATICA
With[{nn=20}, CoefficientList[Series[(1-x)/(1-x-x^2-x^3+x^4), {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Jul 22 2024 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
EXTENSIONS
Definition clarified by Harvey P. Dale, Jul 22 2024
STATUS
approved