|
| |
|
|
A052874
|
|
A simple grammar.
|
|
0
| |
|
|
0, 0, 2, 15, 112, 925, 8556, 88249, 1007056, 12612681, 172092340, 2541367741, 40385290584, 687120886621, 12461362029676, 239945693311185, 4888311943969696, 105038684764873489, 2373935421890157156
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,3
|
|
|
LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 845
|
|
|
FORMULA
| E.g.f.: -x/(-1+x)*(exp(-x/(-1+x))-1)
Recurrence: {a(1)=0, a(0)=0, a(2)=2, (-n^4-6*n^3-11*n^2-6*n)*a(n)+(3*n^3+18*n^2+33*n+18)*a(n+1)+(-3*n^2-14*n-15)*a(n+2)+(n+2)*a(n+3)}
|
|
|
MAPLE
| spec := [S, {C=Sequence(Z, 1 <= card), B=Set(C, 1 <= card), S=Prod(B, C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
|
|
|
CROSSREFS
| Sequence in context: A140637 A022026 A026113 * A074622 A031507 A052861
Adjacent sequences: A052871 A052872 A052873 * A052875 A052876 A052877
|
|
|
KEYWORD
| easy,nonn
|
|
|
AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
|
| |
|
|
