|
| |
|
|
A052718
|
|
A simple context-free grammar in a labeled universe.
|
|
1
| |
|
|
0, 1, 4, 24, 240, 3360, 60480, 1330560, 34594560, 1037836800, 35286451200, 1340885145600, 56317176115200, 2590590101299200, 129529505064960000, 6994593273507840000, 405686409863454720000, 25152557411534192640000
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,3
|
|
|
LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 674
|
|
|
FORMULA
| E.g.f.: -x+1-(1-4*x)^(1/2)
Recurrence: {a(1)=1, a(2)=4, (2-4*n)*a(n)+a(n+1)}
4^(n+1)*GAMMA(n+3/2)/Pi^(1/2)
O.g.f.: 1-x-_2F_0(-1/2,1;;4*x). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 23 2010]
|
|
|
MAPLE
| spec := [S, {B=Union(Z, C), C=Prod(B, B), S=Union(B, C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
|
|
|
MATHEMATICA
| s=2; lst={0, 1}; Do[s+=n*s+s; AppendTo[lst, s], {n, 0, 5!, 4}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Nov 08 2008]
|
|
|
CROSSREFS
| Sequence in context: A034256 A179539 A074598 * A061640 A126391 A006088
Adjacent sequences: A052715 A052716 A052717 * A052719 A052720 A052721
|
|
|
KEYWORD
| easy,nonn
|
|
|
AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
|
| |
|
|
