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 A097628 #10 Jan 15 2019 10:01:34 %S A097628 0,2,15,232,4535,114276,3478083,124625040,5135162607,239298611020, %T A097628 12443586907763,714352426078776,44874695909075799,3061971330141166548, %U A097628 225519631138748009955,17832309102333780001312 %N A097628 Number of rooted directed trees on n nodes with a green root. %C A097628 Ditrees are well-colored directed trees. Well-colored means, each green vertex has at least a red child, each red vertex has no red child. %H A097628 C. Banderier, J.-M. Le Bars and V. Ravelomanana, <a href="https://arxiv.org/abs/math/0411138">Generating functions for kernels of digraphs</a>, arXiv:math/0411138 [math.CO], 2004. %F A097628 E.g.f.: A(x) = C(2x)/2+C(-C(2x)/2), C(x) = e.g.f. of A000169. %t A097628 terms = 16; %t A097628 c[x_] = -LambertW[-x]; %t A097628 A[x_] = c[2x]/2 + c[-c[2x]/2]; %t A097628 CoefficientList[A[x]/x + O[x]^terms, x] Range[terms]! (* _Jean-François Alcover_, Jan 15 2019 *) %Y A097628 Equals A052746(n) - A097627(n). %K A097628 nonn %O A097628 1,2 %A A097628 _Ralf Stephan_, Aug 17 2004