|
| |
|
|
A052832
|
|
A simple grammar.
|
|
0
| |
|
|
0, 0, 2, 6, 36, 240, 2040, 20160, 231840, 3024000, 44271360, 718502400, 12813292800, 249080832000, 5243151513600, 118824010905600, 2884729655808000, 74694359900160000, 2054806272110592000
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,3
|
|
|
LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 797
|
|
|
FORMULA
| E.g.f.: ln((-1+x)/(-1+x+x^2))
Recurrence: {a(1)=0, a(3)=6, a(2)=2, (n^3+3*n^2+2*n)*a(n)+(-4-2*n)*a(n+2)+a(n+3)}
(RootOf(_Z^2-_Z-1)^n*RootOf(_Z^2-_Z-1)+(1-RootOf(_Z^2-_Z-1))^(n+1)-1)*GAMMA(n+1)/RootOf(_Z^2-_Z-1)/(-1+RootOf(_Z^2-_Z-1))
|
|
|
MAPLE
| spec := [S, {B=Prod(Z, C), C=Sequence(Z, 1 <= card), S= Cycle(B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
|
|
|
CROSSREFS
| Sequence in context: A002868 A002869 A052845 * A058583 A075096 A177373
Adjacent sequences: A052829 A052830 A052831 * A052833 A052834 A052835
|
|
|
KEYWORD
| easy,nonn
|
|
|
AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
|
| |
|
|
