|
|
A052567
|
|
E.g.f.: (1-x)^2/(1-3*x+x^2).
|
|
3
|
|
|
1, 1, 6, 48, 504, 6600, 103680, 1900080, 39795840, 937681920, 24548832000, 706966444800, 22210346188800, 755916735974400, 27706219904563200, 1088037381150720000, 45576301518139392000, 2028445209752113152000, 95589693062063456256000, 4754884242802394308608000
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,3
|
|
LINKS
|
|
|
FORMULA
|
E.g.f.: (-1+x)^2/(1-3*x+x^2).
Recurrence: {a(1)=1, a(0)=1, a(2)=6, (n^2+3*n+2)*a(n)+(-6-3*n)*a(n+1)+a(n+2)=0}
Sum(-1/5*(3*_alpha-2)*_alpha^(-1-n), _alpha=RootOf(_Z^2-3*_Z+1))*n!
|
|
MAPLE
|
spec := [S, {S=Sequence(Prod(Z, Sequence(Z), Sequence(Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
|
|
MATHEMATICA
|
With[{nn=20}, CoefficientList[Series[(1-x)^2/(1-3x+x^2), {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Jul 06 2021 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
|
|
STATUS
|
approved
|
|
|
|