|
Search: id:A058790
|
|
|
| A058790 |
|
Number of covers of an unlabeled n-set such that every point of the set is covered by exactly 3 subsets of the cover and that intersection of every 3 subsets of the cover contains at most one point. |
|
+0
3
|
|
| 1, 3, 12, 66, 445, 4279, 53340, 846254, 16333946, 371976963, 9763321109, 290473143807, 9674133467729, 357177322891321, 14503958827502886, 643502334799711633, 31018731336031551119, 1616523352051185316626, 90689288905913623412837, 5456178840303106057314759, 350830170593891706361540379
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
COMMENT
|
Cover may include multiple occurrences of a subset. Also n-rowed binary matrices with distinct rows and all row sums 3.
|
|
REFERENCES
|
For labeled case see Goulden I. P., Jackson D. M., Combinatorial Enumeration, John Wiley and Sons, New York, 1983.
|
|
LINKS
|
Vladeta Jovovic, Formula
|
|
CROSSREFS
|
Cf. A050535, A050913, A058783-A058785, A082789, A082790.
Sequence in context: A086836 A074513 A007871 this_sequence A080599 A120575 A123227
Adjacent sequences: A058787 A058788 A058789 this_sequence A058791 A058792 A058793
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Vladeta Jovovic (vladeta(AT)eunet.rs), Nov 30 2000
|
|
EXTENSIONS
|
More terms from T. Forbes (anthony.d.forbes(AT)googlemail.com), May 24, 2003
|
|
|
Search completed in 0.002 seconds
|
