|
|
A052332
|
|
Number of labeled digraphs where every node has indegree 0 or outdegree 0 and no isolated nodes.
|
|
10
|
|
|
1, 0, 2, 6, 50, 510, 7682, 161406, 4747010, 194342910, 11084390402, 881008805886, 97779099906050, 15178191426486270, 3302331237256396802, 1008694542117649154046, 433286992912494943469570
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,3
|
|
COMMENTS
|
Also labeled graphs with 2-colored nodes with no isolated nodes where black nodes are only connected to white nodes and vice versa.
|
|
LINKS
|
|
|
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, Apr 04 2003
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|