OFFSET
0,2
LINKS
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 537
FORMULA
E.g.f.: (-1+x)/(-1+4*x).
Recurrence: {a(0)=1, a(1)=3, (-4-4*n)*a(n) + a(n+1)=0}.
a(n) = 3*4^(n-1)*n!, n>0.
MAPLE
spec := [S, {S=Sequence(Prod(Sequence(Z), Union(Z, Z, Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
MATHEMATICA
s=3; lst={1, s}; Do[s+=n*s+s; AppendTo[lst, s], {n, 6, 5!, 4}]; lst (* Vladimir Joseph Stephan Orlovsky, Nov 08 2008 *)
With[{nn=20}, CoefficientList[Series[(1-x)/(1-4x), {x, 0, nn}], x] Range[ 0, nn]!] (* Harvey P. Dale, Nov 26 2011 *)
PROG
(PARI) Vec(serlaplace((-1+x)/(-1+4*x)+ O(x^30))) \\ Michel Marcus, Jan 09 2015
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
STATUS
approved