|
Search: id:A052992
|
|
|
| A052992 |
|
A simple regular expression. |
|
+0
3
|
|
| 1, 1, 5, 5, 21, 21, 85, 85, 341, 341, 1365, 1365, 5461, 5461, 21845, 21845, 87381, 87381, 349525, 349525, 1398101, 1398101, 5592405, 5592405, 22369621, 22369621, 89478485, 89478485, 357913941, 357913941, 1431655765, 1431655765
(list; graph; listen)
|
|
|
OFFSET
|
0,3
|
|
|
COMMENT
|
a(n)=sum of square divisors of 2^n. - Paul Barry (pbarry(AT)wit.ie), Oct 13 2005
|
|
LINKS
|
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 1068
|
|
FORMULA
|
G.f.: 1/(-1+4*x^2)/(-1+x)
Recurrence: {a(1)=1, a(0)=1, -4*a(n)-1+a(n+2)}
-1/3+Sum(1/6*(1+4*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+4*_Z^2))
a(n)=sum{k=0..n, 2^k(1+(-1)^k)/2} - Paul Barry (pbarry(AT)wit.ie), Nov 24 2003
|
|
MAPLE
|
spec := [S, {S=Prod(Sequence(Prod(Union(Z, Z), Union(Z, Z))), Sequence(Z))}, unlabeled ]: seq(combstruct[count ](spec, size=n), n=0..20);
|
|
CROSSREFS
|
Sequence in context: A091260 A146043 A116400 this_sequence A147254 A007028 A097336
Adjacent sequences: A052989 A052990 A052991 this_sequence A052993 A052994 A052995
|
|
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 08 2000
|
|
|
Search completed in 0.002 seconds
|
