A084270 Number of labeled 2-chromatic (i.e., chromatic number = 2) graphs on n nodes.

0, 1, 6, 40, 375, 5176, 103236, 2922445, 116011230, 6433447396, 498234407451, 54007795331920, 8213123246906760, 1756336596363006841, 528975889250504033526, 224688018516023267969440, 134708289561117007261966815

Offset

1,3

Links

Table of n, a(n) for n=1..17.

Eric Weisstein's World of Mathematics, n-Chromatic Graph

Formula

a(n) = A047864(n)-1. - Vladeta Jovovic, Jul 31 2003

Crossrefs

Cf. A084271, A084272.

Sequence in context: A000683 A352357 A143342 * A284195 A053677 A204563

Adjacent sequences: A084267 A084268 A084269 * A084271 A084272 A084273

Keyword

nonn

Author

Eric W. Weisstein, May 24 2003

Extensions

More terms from Vladeta Jovovic, Jul 31 2003

One further term from David Wasserman, Dec 13 2004

Status

approved