|
Search: id:A113920
|
|
|
| A113920 |
|
G.f.: (x^3 - x + 1)^3/(x^3*(1 - x)^3). |
|
+0
1
|
|
| 1, 0, 0, 3, 3, 3, 6, 9, 12, 16, 21, 27, 34, 42, 51, 61, 72, 84, 97, 111, 126, 142, 159, 177, 196, 216, 237, 259, 282, 306, 331, 357, 384, 412, 441, 471, 502, 534, 567, 601, 636, 672, 709, 747, 786, 826, 867, 909, 952, 996, 1041, 1087, 1134, 1182, 1231, 1281, 1332, 1384, 1437
(list; graph; listen)
|
|
|
OFFSET
|
-3,4
|
|
|
COMMENT
|
Series expansion of elliptical invariant for a cubic anharmonic group. Suggested by the anharmonic group elliptical invariant A078907.
If Y is a 4-subset of an n-set X then, for n>=7, a(n-3) is the number of 2-subsets of X which have no exactly one element in common with Y. - Milan R. Janjic (agnus(AT)blic.net), Dec 28 2007
|
|
REFERENCES
|
McKean and Moll, Elliptic Curves, 1997, Cambridge University Press, page 20.
|
|
FORMULA
|
a(n-7)=1/2*n^2-9/2*n+16, n=7,8,9,... - Milan R. Janjic (agnus(AT)blic.net), Dec 28 2007
|
|
MATHEMATICA
|
b = ReplacePart[Table[Coefficient[Series[(x^3 - x + 1)^3/(x^3*(1 - x)^3), {x, 0, 30}], x^n], {n, -3, 30}], 3, 4]
|
|
CROSSREFS
|
Cf. A078907.
Sequence in context: A124449 A141094 A132972 this_sequence A081848 A079988 A061021
Adjacent sequences: A113917 A113918 A113919 this_sequence A113921 A113922 A113923
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Roger L. Bagula (rlbagulatftn(AT)yahoo.com), Jan 29 2006
|
|
EXTENSIONS
|
Edited by njas, Apr 21 2007
|
|
|
Search completed in 0.002 seconds
|
