%I A076278
%S A076278 0,1,2,6,12,34,87,302,1118,5478,32302,251134,2527711,33985852,611846939,
%T A076278 14864650923,488222721991,21712049275197,1308300679611468,
%U A076278 106897965189674290
%N A076278 Number of 2-chromatic (i.e. chromatic number equals 2) simple graphs 
               on n nodes.
%H A076278 Keith M. Briggs, <a href="http://keithbriggs.info/cgt.html">Combinatorial 
               Graph Theory</a>
%H A076278 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               n-ChromaticGraph.html">n-Chromatic Graph</a>
%F A076278 a(n) = A033995(n)-1.
%Y A076278 Cf. A076279, A076280, A076281, A076282, A115597.
%Y A076278 Sequence in context: A096610 A164099 A088808 this_sequence A099576 A026549 
               A120766
%Y A076278 Adjacent sequences: A076275 A076276 A076277 this_sequence A076279 A076280 
               A076281
%K A076278 nonn,more
%O A076278 1,3
%A A076278 Eric Weisstein (eric(AT)weisstein.com), Oct 06, 2002
%E A076278 More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Jul 31 2003