|
|
A052580
|
|
E.g.f. (1-2x)/(1-2x-x^2).
|
|
1
|
|
|
1, 0, 2, 12, 120, 1440, 20880, 352800, 6814080, 148055040, 3574368000, 94922150400, 2749948185600, 86306508288000, 2917072801843200, 105636550795776000, 4080467097907200000, 167469023145295872000
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,3
|
|
LINKS
|
|
|
FORMULA
|
E.g.f.: (-1+2*x)/(-1+2*x+x^2)
D-finite recurrence: {a(1)=0, a(0)=1, (-2-n^2-3*n)*a(n)+(-4-2*n)*a(n+1)+a(n+2)=0.}
Sum(1/4*(-1+3*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+2*_Z+_Z^2))*n!
|
|
MAPLE
|
spec := [S, {S=Sequence(Prod(Z, Z, Sequence(Union(Z, Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
|
|
MATHEMATICA
|
With[{nn=20}, CoefficientList[Series[(1-2x)/(1-2x-x^2), {x, 0, nn}], x] Range[ 0, nn]!] (* Harvey P. Dale, Dec 05 2018 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
|
|
STATUS
|
approved
|
|
|
|