

A140636


Number of unlabeled complex components with n nodes.


2



0, 0, 0, 2, 13, 93, 809, 11005, 260793, 11715808, 1006698524, 164059824899, 50335907853919, 29003487462805642, 31397381142761123838, 63969560113225175845492, 245871831682084026518599099, 1787331725248899088890197955308, 24636021429399867655322650752269938
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OFFSET

1,4


COMMENTS

We can find in "The Birth of the Giant Component", p. 2, see the first link:
"As each of the random graphs evolved, the story went, never once was there more than a single 'complex' component; i.e. there never were two or more components present simultaneously that were neither trees nor unicyclic."
So a complex component is a connected graph that is neither a tree nor an unicyclic graph.


LINKS

Table of n, a(n) for n=1..19.
Svante Janson, Donald E. Knuth, Tomasz Luczak and Boris Pittel, The Birth of the Giant Component, [DOI], Rand. Struct. Alg. 4 (3) (1993) 233358
N. J. A. Sloane, Illustration of initial terms of A001349.


FORMULA

For n < 3, a(n) = A001349(n)  A000055(n). a(n) = A001349(n)  A005703(n).


EXAMPLE

a(4)=2. See the two complex components with 4 nodes in the Sloane illustration.


CROSSREFS

Cf. A001349, A000055, A001429, A005703.
Sequence in context: A199489 A300764 A209470 * A282724 A104255 A118352
Adjacent sequences: A140633 A140634 A140635 * A140637 A140638 A140639


KEYWORD

nonn


AUTHOR

Washington Bomfim, May 20 2008


STATUS

approved



