OFFSET
0,3
LINKS
Robert Israel, Table of n, a(n) for n = 0..448
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 512
FORMULA
E.g.f.: 1/(-1+x)/(-1+x^3)
Recurrence: {a(1)=1, a(0)=1, a(2)=2, (-14*n-n^3-7*n^2-8)*a(n)+(-2-n)*a(n+1)+a(n+3)-a(n+2)=0}
(1/3*n+2/3+Sum(1/9*(-1+_alpha)*_alpha^(-1-n), _alpha=RootOf(_Z^2+_Z+1)))*n!
a(n) = n!*A008620(n). - R. J. Mathar, Nov 27 2011
MAPLE
spec := [S, {S=Prod(Sequence(Prod(Z, Z, Z)), Sequence(Z))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
# Alternative:
f:= gfun:-rectoproc({ a(1)=1, a(0)=1, a(2)=2, (-14*n-n^3-7*n^2-8)*a(n)+(-2-n)*a(n+1)+a(n+3)-a(n+2)=0}, a(n), remember):
map(f, [$0..30]); # Robert Israel, Sep 25 2019
MATHEMATICA
With[{nn=20}, CoefficientList[Series[1/((1-x)(1-x^3)), {x, 0, nn}], x]Range[0, nn]!] (* Harvey P. Dale, Aug 25 2012 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
STATUS
approved