|
| |
|
|
A052585
|
|
E.g.f. 1/(1-x-2x^2).
|
|
3
| |
|
|
1, 1, 6, 30, 264, 2520, 30960, 428400, 6894720, 123742080, 2478470400, 54486432000, 1308153369600, 34005760588800, 952248474777600, 28566146568960000, 914137612996608000, 31080323154456576000
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,3
|
|
|
COMMENTS
| Laguerre transform is A052563. [From Paul Barry (pbarry(AT)wit.ie), Aug 08 2008]
|
|
|
LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 530
|
|
|
FORMULA
| E.g.f.: -1/(-1+x+2*x^2)
Recurrence: {a(1)=1, a(0)=1, (-2*n^2-6*n-4)*a(n)+(-2-n)*a(n+1)+a(n+2)=0}
Sum(1/9*(1+4*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+_Z+2*_Z^2))*n!
a(n)=n!*A001045(n+1). [From Paul Barry (pbarry(AT)wit.ie), Aug 08 2008] a(n) = D^n(1/(1-x)) evaluated at x = 0, where D is the operator sqrt(1+8*x)*d/dx. Cf. A080599 and A005442. - Peter Bala, Dec 07 2011
|
|
|
MAPLE
| spec := [S, {S=Sequence(Union(Z, Prod(Z, Union(Z, Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
|
|
|
CROSSREFS
| A080599 and A005442.
Sequence in context: A009689 A133668 A121772 * A051821 A099031 A066108
Adjacent sequences: A052582 A052583 A052584 * A052586 A052587 A052588
|
|
|
KEYWORD
| easy,nonn
|
|
|
AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
|
| |
|
|
