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%I #7 Oct 27 2012 11:06:23
%S 1,0,1,3,20,240,5224,209832,15956480,2346694080,675730946176,
%T 383352300553728,430056580863004160,956441558748755089920,
%U 4224552623552204307349504,37106534862502586820794145792,648740342428921612538202170408960,22591362491840723496251402052982210560,1567817841212459564387810603215973889703936
%N Number of simple labeled graphs on n nodes with an even number of components.
%H Alois P. Heinz, <a href="/A218374/b218374.txt">Table of n, a(n) for n = 0..50</a>
%F E.g.f.: cosh(A(x)-1) where A(x) is the e.g.f. for A001187.
%t nn=18;a=Sum[2^Binomial[n,2]x^n/n!,{n,0,nn}];Range[0,nn]!CoefficientList[Series[Cosh[ Log[a]],{x,0,nn}],x]
%Y Cf. A218375.
%K nonn
%O 0,4
%A _Geoffrey Critzer_, Oct 27 2012