A084270 - OEIS

%I #12 Feb 16 2025 08:32:49

%S 0,1,6,40,375,5176,103236,2922445,116011230,6433447396,498234407451,

%T 54007795331920,8213123246906760,1756336596363006841,

%U 528975889250504033526,224688018516023267969440,134708289561117007261966815

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

%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/n-ChromaticGraph.html">n-Chromatic Graph</a>

%F a(n) = A047864(n)-1. - _Vladeta Jovovic_, Jul 31 2003

%Y Cf. A084271, A084272.

%K nonn

%O 1,3

%A _Eric W. Weisstein_, May 24 2003

%E More terms from _Vladeta Jovovic_, Jul 31 2003

%E One further term from _David Wasserman_, Dec 13 2004