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 A097172 #7 Aug 26 2016 02:44:04
%S A097172 3,4,185,1026,30457,362664,10245825,195060070,5907674201,153676400076,
%T A097172 5199628119985,169205814335754,6462995557999905,249877775352089296,
%U A097172 10749867848389013249,478345428286978038606,23013713995857481324969
%N A097172 Total number of brown nodes among tricolored labeled trees on n nodes.
%H A097172 S. Coulomb and M. Bauer, <a href="http://arXiv.org/abs/math.CO/0407456">On vertex covers, matchings and random trees</a>
%F A097172 E.g.f.: A(x) = T(x)+T(-T(x))-T(-T(x))^2, with T(x)=Sum[k=1..inf, A000169(k)/k!*x^k].
%F A097172 a(n) = -n^(n-1) * {1 + Sum[l=1..n, (-l/n)^l*(2/l-1)*C(n, l)]}.
%F A097172 a(n) ~ (1-2*LambertW(1)^2)*n^(n-1)/(1+LambertW(1)). - _Vaclav Kotesovec_, Aug 26 2016
%t A097172 Drop[CoefficientList[Series[-LambertW[-x] - LambertW[-LambertW[-x]]- LambertW[-LambertW[-x]]^2, {x, 0, 20}], x] * Range[0, 20]!, 3] (* _Vaclav Kotesovec_, Aug 26 2016 *)
%Y A097172 Equals A000169(n)-A097174(n)-A097173(n).
%Y A097172 Cf. A097170, A097171, A097173, A097174, A000272.
%K A097172 nonn
%O A097172 3,1
%A A097172 _Ralf Stephan_, Jul 30 2004