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 A182166 #22 Sep 05 2022 05:25:25
%S A182166 1,3,12,80,960,21504,917504,75497472,12079595520,3779571220480,
%T A182166 2322168557862912,2810246167479189504,6714614842830276788224,
%U A182166 31734302764884015836037120,297105609428491265975789813760,5516815412193254355313652349796352
%N A182166 The total number of components of size 2 over all simple labeled graphs on n nodes.
%H A182166 Alois P. Heinz, <a href="/A182166/b182166.txt">Table of n, a(n) for n = 2..50</a>
%F A182166 E.g.f.: x^2/2 * G(x) where G(x) is e.g.f. for A006125.
%F A182166 a(n) = C(n,2) * 2^C(n-2,2). - _Alois P. Heinz_, Apr 16 2012
%p A182166 a:= n-> binomial(n, 2) *2^binomial(n-2, 2):
%p A182166 seq (a(n), n=2..20); # _Alois P. Heinz_, Apr 16 2012
%t A182166 nn = 20; g = Sum[2^Binomial[n, 2] x^n/n!, {n, 0, nn}]; Drop[Range[0, nn]! CoefficientList[Series[x^2/2 g, {x, 0, nn}], x], 2]
%o A182166 (Magma) B:=Binomial; [B(n,2)*2^B(n-2,2): n in [2..20]]; // _G. C. Greubel_, Sep 04 2022
%o A182166 (SageMath) b=binomial; [b(n,2)*2^b(n-2,2) for n in (2..20)] # _G. C. Greubel_, Sep 04 2022
%Y A182166 Cf. A000217, A006125.
%K A182166 nonn
%O A182166 2,2
%A A182166 _Geoffrey Critzer_, Apr 15 2012