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%I #8 Apr 11 2017 10:34:51
%S 1,1,12,815,157762,64916201,48508522364
%N Chromatic invariant of the n-Andrásfai graph.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/AndrasfaiGraph.html">Andrásfai Graph</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/ChromaticInvariant.html">Chromatic Invariant</a>
%t Table[Derivative[1][ChromaticPolynomial[CirculantGraph[3 n - 1, Range[1, 3 n, 3]]]][1], {n, 6}] // Abs (* _Eric W. Weisstein_, Apr 11 2017 *)
%o (Sage) def a(n) : return graphs.CirculantGraph(3*n-1, range(1, 3*n, 3)) .chromatic_polynomial().derivative()(1).abs()
%Y Cf. A193126.
%K nonn,hard,more
%O 1,3
%A _Eric M. Schmidt_, Dec 31 2016
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