|
Search: id:A052332
|
|
|
| A052332 |
|
Number of labeled digraphs where every node has indegree 0 or outdegree 0 and no isolated nodes. |
|
+0
7
|
|
| 1, 0, 2, 6, 50, 510, 7682, 161406, 4747010, 194342910, 11084390402, 881008805886, 97779099906050, 15178191426486270, 3302331237256396802, 1008694542117649154046, 433286992912494943469570
(list; graph; listen)
|
|
|
OFFSET
|
0,3
|
|
|
COMMENT
|
Also labeled graphs with 2-colored nodes with no isolated nodes where black nodes are only connected to white nodes and vice versa.
|
|
FORMULA
|
a(n) = sum_{k=0..n} (-1)^(n-k)*binomial(n, k)*A001831(k)
a(n) = Sum_{k=0..n} binomial(n, k)*(2^k-2)^(n-k). - Vladeta Jovovic (vladeta(AT)eunet.rs), Apr 04 2003
|
|
CROSSREFS
|
Cf. A001831, A002031, A047863.
Sequence in context: A080310 A103990 A079835 this_sequence A134047 A078464 A108905
Adjacent sequences: A052329 A052330 A052331 this_sequence A052333 A052334 A052335
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Christian G. Bower (bowerc(AT)usa.net), Dec 15 1999.
|
|
EXTENSIONS
|
Last 4 terms corrected by Vladeta Jovovic (vladeta(AT)eunet.rs), Apr 04 2003
|
|
|
Search completed in 0.002 seconds
|
