|
Search: id:A052646
|
|
|
| A052646 |
|
A simple regular expression in a labeled universe. |
|
+0
1
|
|
| 1, 2, 8, 42, 288, 2400, 23760, 272160, 3548160, 51891840, 841881600, 15008716800, 291711974400, 6139842508800, 139136552755200, 3377722892544000, 87457261731840000, 2405869763641344000
(list; graph; listen)
|
|
|
OFFSET
|
0,2
|
|
|
LINKS
|
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 592
|
|
FORMULA
|
E.g.f.: 1/(-1+x)/(-1+x+x^2)
Recurrence: {a(0)=1, a(1)=2, a(2)=8, (n^3+6*n^2+11*n+6)*a(n)+(-2*n-6)*a(n+2)+a(n+3)}
(-1+Sum(1/5*(4+3*_alpha)*_alpha^(-1-n), _alpha =RootOf(-1+_Z+_Z^2)))*n!
n!*Sum(k=0, n, F(n+1)), F(n) = A000045(n).
|
|
MAPLE
|
spec := [S, {S=Prod(Sequence(Z), Sequence(Union(Z, Prod(Z, Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
|
|
CROSSREFS
|
Sequence in context: A121635 A002874 A078592 this_sequence A002856 A093461 A153524
Adjacent sequences: A052643 A052644 A052645 this_sequence A052647 A052648 A052649
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
|
|
|
Search completed in 0.002 seconds
|
