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 A193489 #8 Feb 17 2018 21:12:17 %S A193489 0,0,0,0,0,1,1,7,13,55,127,435,1110,3458,9261,27460,75305,217619, %T A193489 603618,1720712,4799095,13580179,37979149,107045222,299800569, %U A193489 843242264,2363693561,6641675073,18628827667,52325428340 %N A193489 Number of rooted trees with n nodes and omega-valency 4. %C A193489 See A003120 for definitions. %H A193489 J.-C. Arditti, <a href="http://dx.doi.org/10.1016/0012-365X(73)90135-0">Dénombrement des arborescences dont le graphe de comparabilité est Hamiltonien</a>, Discrete Math., 5 (1973), 189-200. %Y A193489 Cf. A003120, A193487, A193489, A193490, A193491. %K A193489 nonn %O A193489 1,8 %A A193489 _N. J. A. Sloane_, Jul 27 2011