OFFSET
0,3
LINKS
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 541
FORMULA
E.g.f.: (-1-x^4+x^5)/(-1+x)
Recurrence: {a(1)=1, a(0)=1, (-1-n)*a(n)+a(n+1)=0, a(3)=6, a(2)=2, a(5)=120, a(4)=48}
n!, n>4.
MAPLE
spec := [S, {S=Union(Sequence(Z), Prod(Z, Z, Z, Z))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
MATHEMATICA
With[{nn=30}, CoefficientList[Series[(1+x^4-x^5)/(1-x), {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Dec 25 2011 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
STATUS
approved