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%I #16 May 17 2017 08:57:19
%S 0,1,6,33,170,1170,10962,172844,4944024,270116280,28022441260,
%T 5448008695536,1969579223350128,1321964082404214704,
%U 1649890513414726210320,3840060942271653473695680,16723638762440239422492944768,136749695973639295091912681599872
%N Total number of edges in the distinct simple graphs on n nodes.
%C a(n) = A000088(n)*n(n-1)/4.
%C a(n) = A000088(n)*A064038(n)/A014695(n).
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/SimpleGraph.html">Simple Graph</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/GraphEdge.html">Graph Edge</a>
%t << Combinatorica`; Table[D[GraphPolynomial[n, x], x] /. x -> 1, {n, 18}] (* _Geoffrey Critzer_, Sep 29 2012 *)
%t << Combinatorica`; Table[Binomial[n, 2] NumberOfGraphs[n]/2, {n, 18}] (* _Eric W. Weisstein_, May 17 2017 *)
%Y Cf. A000088, A014695, A064038.
%K nonn
%O 1,3
%A _Eric W. Weisstein_, Jul 15 2003
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