|
Search: id:A052545
|
|
|
| A052545 |
|
A simple regular expression. |
|
+0
1
|
|
| 1, 1, 4, 11, 32, 92, 265, 763, 2197, 6326, 18215, 52448, 151018, 434839, 1252069, 3605189, 10380728, 29890115, 86065156, 247814740, 713554105, 2054597159, 5915976737, 17034376106, 49048531159, 141229616740, 406654474114
(list; graph; listen)
|
|
|
OFFSET
|
0,3
|
|
|
LINKS
|
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 481
|
|
FORMULA
|
G.f.: (-1+x)^2/(1-3*x+x^3)
Recurrence: {a(1)=1, a(0)=1, a(2)=4, a(n)-3*a(n+2)+a(n+3)}
Sum(-1/9*(-1+2*_alpha^2-2*_alpha)*_alpha^(-1-n), _alpha=RootOf(1-3*_Z+_Z^3))
|
|
MAPLE
|
spec := [S, {S=Sequence(Prod(Z, Union(Z, Sequence(Z)), Sequence(Z)))}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..20);
|
|
CROSSREFS
|
Sequence in context: A027153 A034754 A038747 this_sequence A025268 A034745 A099159
Adjacent sequences: A052542 A052543 A052544 this_sequence A052546 A052547 A052548
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
|
|
EXTENSIONS
|
More terms from James A. Sellers (sellersj(AT)math.psu.edu), Jun 06 2000
|
|
|
Search completed in 0.002 seconds
|
