%I #18 Jan 20 2020 17:10:19

%S 0,0,0,1,4,31,318,5366,155291,7855628,675054876

%N Number of 4-chromatic (i.e., chromatic number equals 4) simple graphs on n nodes.

%H Keith M. Briggs, <a href="http://keithbriggs.info/cgt.html">Combinatorial Graph Theory</a>

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

%Y Column k=4 of A084268.

%Y Cf. A076278, A076279, A076281, A076282.

%K nonn,more

%O 1,5

%A _Eric W. Weisstein_, Oct 06 2002

%E a(10) from _Keith Briggs_, Feb 24 2006

%E a(11) from _Michael Sollami_, Jan 28 2012