|
| |
|
|
A063759
|
|
Spherical growth series for modular group.
|
|
5
| |
|
|
1, 3, 4, 6, 8, 12, 16, 24, 32, 48, 64, 96, 128, 192, 256, 384, 512, 768, 1024, 1536, 2048, 3072, 4096, 6144, 8192, 12288, 16384, 24576, 32768, 49152, 65536, 98304, 131072, 196608, 262144, 393216, 524288, 786432, 1048576, 1572864, 2097152
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,2
|
|
|
REFERENCES
| P. de la Harpe, Topics in Geometric Group Theory, Univ. Chicago Press, 2000, p. 156.
|
|
|
LINKS
| Index entries for sequences related to modular groups
|
|
|
FORMULA
| G.f.: (1+3*x+2*x^2)/(1-2*x^2).
a(n)=2*a(n-2), n>2 [From Harvey P. Dale, Oct 22 2011]
|
|
|
MATHEMATICA
| CoefficientList[Series[(1+3*x+2*x^2)/(1-2*x^2), {x, 0, 40}], x](* Jean-François Alcover Mar 21 2011 *)
Join[{1}, Transpose[NestList[{Last[#], 2First[#]}&, {3, 4}, 40]][[1]]] (* From Harvey P. Dale, Oct 22 2011 *)
|
|
|
CROSSREFS
| Cf. A054886, A029744.
Sequence in context: A147606 A085147 A145751 * A163978 A204658 A139041
Adjacent sequences: A063756 A063757 A063758 * A063760 A063761 A063762
|
|
|
KEYWORD
| nonn,nice,easy
|
|
|
AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Aug 14 2001
|
| |
|
|
