|
Search: id:A052590
|
|
|
| A052590 |
|
A simple regular expression in a labeled universe. |
|
+0
1
|
|
| 1, 3, 20, 204, 2784, 47520, 973440, 23264640, 635443200, 19525847040, 666654105600, 25037094297600, 1025783842406400, 45529186384281600, 2176249118883840000, 111452688851632128000, 6088372509440212992000
(list; graph; listen)
|
|
|
OFFSET
|
0,2
|
|
|
LINKS
|
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 535
|
|
FORMULA
|
E.g.f.: -(-1+x)/(1-4*x+2*x^2)
Recurrence: {a(0)=1, a(1)=3, (2*n^2+6*n+4)*a(n)+(-4*n-8)*a(n+1)+a(n+2)}
Sum(1/4*_alpha^(-1-n), _alpha=RootOf(1-4*_Z+2*_Z^2))*n!
|
|
MAPLE
|
spec := [S, {S=Sequence(Union(Z, Z, Prod(Z, Sequence(Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
|
|
CROSSREFS
|
Sequence in context: A087152 A054361 A052595 this_sequence A081209 A014068 A006963
Adjacent sequences: A052587 A052588 A052589 this_sequence A052591 A052592 A052593
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
|
|
|
Search completed in 0.002 seconds
|
