|
Search: id:A052989
|
|
|
| A052989 |
|
A simple regular expression. |
|
+0
1
|
|
| 1, 0, 1, 1, 3, 3, 7, 10, 19, 29, 52, 84, 145, 239, 407, 678, 1146, 1918, 3232, 5421, 9121, 15314, 25749, 43252, 72701, 122146, 205282, 344931, 579662, 974038, 1636836, 2750523, 4622090, 7766989, 13051877, 21932553, 36855997, 61933449, 104074334
(list; graph; listen)
|
|
|
OFFSET
|
0,5
|
|
|
LINKS
|
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 1063
|
|
FORMULA
|
G.f.: -(-1+x)/(1-x-x^2-x^4+x^5)
Recurrence: {a(1)=0, a(0)=1, a(2)=1, a(3)=1, a(4)=3, a(n)-a(n+1)-a(n+3)-a(n+4)+a(n+5)}
Sum(-1/8519*(-389-2111*_alpha+619*_alpha^2-358*_alpha^3+541*_alpha^4)*_alpha^(-1-n), _alpha=RootOf(1-_Z-_Z^2-_Z^4+_Z^5))
|
|
MAPLE
|
spec := [S, {S=Sequence(Prod(Union(Prod(Z, Z), Sequence(Z)), Z, Z))}, unlabeled ]: seq(combstruct[count ](spec, size=n), n=0..20);
|
|
CROSSREFS
|
Sequence in context: A157933 A013915 A136445 this_sequence A022403 A082550 A036056
Adjacent sequences: A052986 A052987 A052988 this_sequence A052990 A052991 A052992
|
|
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
|
