|
Search: id:A003027
|
|
|
| A003027 |
|
Number of weakly connected digraphs with n nodes.
(Formerly M3161)
|
|
+0
10
|
|
| 1, 3, 54, 3834, 1027080, 1067308488, 4390480193904, 72022346388181584, 4721717643249254751360, 1237892809110149882059440768, 1298060596773261804821355107253504
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
REFERENCES
|
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
R. W. Robinson, Counting labeled acyclic digraphs, pp. 239-273 of F. Harary, editor, New Directions in the Theory of Graphs. Academic Press, NY, 1973.
|
|
LINKS
|
T. D. Noe, Table of n, a(n) for n=1..30
|
|
FORMULA
|
a(n) = A062738(n)/2^n, since binary relations = digraphs with loops. - Ralf Stephan and Vladeta Jovovic, Mar 24 2004
|
|
CROSSREFS
|
Sequence in context: A091796 A006025 A049414 this_sequence A054545 A158103 A157568
Adjacent sequences: A003024 A003025 A003026 this_sequence A003028 A003029 A003030
|
|
KEYWORD
|
nonn,easy,nice
|
|
AUTHOR
|
N. J. A. Sloane (njas(AT)research.att.com).
|
|
EXTENSIONS
|
Corrected and extended by Vladeta Jovovic, Goran Kilibarda (vladeta(AT)eunet.rs).
|
|
|
Search completed in 0.002 seconds
|
