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 A036251 #18 Jan 28 2019 14:00:24
%S A036251 1,2,3,3,7,14,35,85,231,633,1845,5461,16707,51945,164695,529077,
%T A036251 1722279,5664794,18813369,62996850,212533226,721792761,2466135375,
%U A036251 8471967938,29249059293,101440962296,353289339927,1235154230060
%N A036251 Number of trees with 2-colored leaves.
%H A036251 <a href="/index/Tra#trees">Index entries for sequences related to trees</a>
%F A036251 G.f.: B(x) + B(x)^2/2 + B(x^2)/2 - B(x)*(B(x)-x), where B(x) is g.f. for A029856.
%t A036251 max = 30; B[_] = 1; Do[B[x_] = x*Exp[Sum[(B[x^k] + x^k)/k + O[x]^n, {k, 1, n}]] // Normal, {n, 1, max}]; A[x_] = 1 + x + x^2 + B[x] - B[x]^2/2 + B[x^2]/2; CoefficientList[A[x] + O[x]^max, x] (* _Jean-François Alcover_, Jan 28 2019 *)
%Y A036251 Essentially the same as A036250. Cf. A038054.
%K A036251 nonn
%O A036251 0,2
%A A036251 _Christian G. Bower_, Nov 15 1998