|
Search: id:A055538
|
|
|
| A055538 |
|
Number of asymmetric types of (3,n)-hypergraphs without isolated nodes, under action of symmetric group S_3; asymmetric n-covers of an unlabeled 3-set. |
|
+0
1
|
|
| 4, 20, 65, 170, 383, 779, 1470, 2611, 4418, 7182, 11283, 17213, 25601, 37230, 53074, 74327, 102434, 139133, 186501, 246988, 323479, 419344, 538492, 685438, 865376, 1084236, 1348777, 1666664, 2046551, 2498179, 3032482, 3661673, 4399374
(list; graph; listen)
|
|
|
OFFSET
|
3,1
|
|
|
COMMENT
|
Cover may include both empty sets and multiple occurrences of a subset.
|
|
FORMULA
|
G.f. : (1/(1-x)^8-3/(1-x)^4/(1-x^2)^2+2/(1-x)^2/(1-x^3)^2-3/(1-x)^4+3/(1-x)^2/(1-x^2)+6/(1-x)^2-6/(1-x))/6.
|
|
EXAMPLE
|
There are 4 asymmetric (3,3)-hypergraphs without isolated nodes: {{1,2},{1,2},{1,3}}, {{1},{1,2},{1,2,3}}, {{1},{1,2},{2,3}}, {{1},{2},{1,3}}.
|
|
CROSSREFS
|
Cf. A005745.
Sequence in context: A018211 A135507 A131479 this_sequence A123613 A006740 A061981
Adjacent sequences: A055535 A055536 A055537 this_sequence A055539 A055540 A055541
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Vladeta Jovovic (vladeta(AT)eunet.rs), Jul 09 2000
|
|
EXTENSIONS
|
More terms from James A. Sellers (sellersj(AT)math.psu.edu), Jul 11 2000
|
|
|
Search completed in 0.002 seconds
|
