This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A228596 #12 Aug 28 2013 05:03:53 %S A228596 1,1,2,4,48,944,32288,2089312,268215040,68708556288,35183367427072, %T A228596 36028619925285888,73786915826515503104,302231414653310649337856, %U A228596 2475880026112961032035266560,40564819073011099018919903485952,1329227995107917459000217502447435776 %N A228596 The number of simple labeled graphs on n nodes with no components of size 3. %H A228596 Alois P. Heinz, <a href="/A228596/b228596.txt">Table of n, a(n) for n = 0..50</a> %F A228596 E.g.f.: exp(-4*x^3/3!)*A(x) where A(x) is the e.g.f. for A006125. %F A228596 Generally, the e.g.f. for the number of simple labeled graphs on n nodes with no size k components is exp( -A001187(k)*x^k/k! ) * A(x) with A(x) as above. %t A228596 nn = 15; g = Sum[2^Binomial[n, 2] x^n/n!, {n, 0, nn}]; %t A228596 Range[0, nn]! CoefficientList[Series[Exp[-4 x^3/3!] g, {x, 0, nn}], x] %Y A228596 Cf. A093352, A006129. %K A228596 nonn %O A228596 0,3 %A A228596 _Geoffrey Critzer_, Aug 27 2013