|
| |
|
|
A052604
|
|
E.g.f. (1-x)/(1-2x-x^3+x^4).
|
|
0
| |
|
|
1, 1, 4, 30, 240, 2520, 32400, 478800, 8104320, 154586880, 3273177600, 76241088000, 1937561472000, 53340660172800, 1581414202368000, 50234310846720000, 1702089880178688000, 61276407362666496000
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,3
|
|
|
LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 549
|
|
|
FORMULA
| E.g.f.: -(-1+x)/(1-2*x-x^3+x^4)
Recurrence: {a(1)=1, a(0)=1, a(2)=4, (n^4+35*n^2+50*n+24+10*n^3)*a(n)+(-n^3-9*n^2-26*n-24)*a(n+1)+(-2*n-8)*a(n+3)+a(n+4)=0, a(3)=30}
Sum(-1/643*(-94-127*_alpha-22*_alpha^2+75*_alpha^3)*_alpha^(-1-n), _alpha=RootOf(1-2*_Z-_Z^3+_Z^4))*n!
a(n)= n!*A052540(n). - R. J. Mathar, Nov 27 2011
|
|
|
MAPLE
| spec := [S, {S=Sequence(Prod(Z, Union(Sequence(Z), Prod(Z, Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
|
|
|
CROSSREFS
| Sequence in context: A000313 A082144 A137971 * A038225 A086452 A091527
Adjacent sequences: A052601 A052602 A052603 * A052605 A052606 A052607
|
|
|
KEYWORD
| easy,nonn
|
|
|
AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
|
| |
|
|
