%I A076280
%S A076280 0,0,0,1,4,31,318,5366,155291,7855628
%N A076280 Number of 4-chromatic (i.e. chromatic number equals 4) simple graphs 
               on n nodes.
%H A076280 Keith M. Briggs, <a href="http://keithbriggs.info/cgt.html">Combinatorial 
               Graph Theory</a>
%H A076280 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               n-ChromaticGraph.html">n-Chromatic Graph</a>
%Y A076280 Cf. A076278, A076279, A076281, A076282.
%Y A076280 Sequence in context: A000858 A003436 A114475 this_sequence A141005 A122400 
               A107725
%Y A076280 Adjacent sequences: A076277 A076278 A076279 this_sequence A076281 A076282 
               A076283
%K A076280 nonn
%O A076280 1,5
%A A076280 Eric Weisstein (eric(AT)weisstein.com), Oct 06, 2002
%E A076280 a(10) from Keith Briggs, Mar 14 2006.