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 A323876 #18 Feb 26 2019 05:02:54
%S A323876 0,0,1,6,55,825,20818,925036,76321756,12143833740,3786364993664,
%T A323876 2323363153263768,2810644049356050752,6714880790313869814368,
%U A323876 31734660624638397560681792,297106568651256947892439231872,5516820501457062391874183605225216,203371936690880564729559424288326233856,14896201998273652941883043518617399703696384
%N A323876 Number of labeled graphs on n nodes with three connected components.
%D A323876 F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, 1973, section 1.2.
%H A323876 Marko Riedel et al., <a href="https://math.stackexchange.com/questions/3094635/">Proof of recurrence relation.</a>
%H A323876 Marko Riedel, <a href="/A323876/a323876.maple.txt">Maple implementation of memoized recurrence.</a>
%F A323876 a(n) = A143543(n+1, 3) for n >= 1 and a(0) = 0.
%F A323876 E.g.f.: log(Sum_{q>=0} 2^binomial(q, 2)*z^q/q!)^3/3!.
%Y A323876 Cf. A143543, A323875, A323877.
%K A323876 nonn
%O A323876 1,4
%A A323876 _Marko Riedel_, Feb 05 2019