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%I #16 Aug 14 2019 22:22:01
%S 1,0,1,1,0,1,2,1,0,1,7,2,1,0,1,23,7,2,1,0,1,122,23,7,2,1,0,1,888,122,
%T 23,7,2,1,0,1,11302,888,122,23,7,2,1,0,1,262322,11302,888,122,23,7,2,
%U 1,0,1,11730500,262322,11302,888,122,23,7,2,1,0,1
%N Triangular array read by rows: T(n,k) is the number of unlabeled simple graphs with n nodes that have exactly k isolated nodes, (n>=0, 0<=k<=n).
%C Row sums = A000088.
%C Sum_{k=1..n} T(n,k)*k = A006897(n).
%C Column k = 0 is A002494.
%F O.g.f.: A(x)/(1-y*x) where A(x) is o.g.f. for A002494.
%e 1,
%e 0, 1,
%e 1, 0, 1,
%e 2, 1, 0, 1,
%e 7, 2, 1, 0, 1,
%e 23, 7, 2, 1, 0, 1,
%e 122, 23, 7, 2, 1, 0, 1
%t Needs["Combinatorica`"]; nn=10; s=Sum[NumberOfGraphs[n]x^n, {n,0,nn}]; CoefficientList[Series[s (1-x)/(1-y x), {x,0,nn}], {x,y}] //Grid
%Y Cf. A000088, A002494, A006897.
%K nonn,tabl
%O 0,7
%A _Geoffrey Critzer_, Oct 09 2012
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