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%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
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