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 A228855 #16 Jun 20 2018 19:18:36
%S A228855 2,3,5,8,11,13,18,19,21,27,29,30,31,34,41,44,46,47,49,50,55,65,67,68,
%T A228855 71,73,75,76,79,80,81,89,100,101,106,108,109,111,112,115,116,117,119,
%U A228855 121,123,128,129,131,144,153,157,163,165,166,171,172,173,175,176
%N A228855 Nodes of tree generated as follows: (2,3) is an edge, and if (x,y) is an edge, then (y,y+x) and (y,2y+x) are edges.
%H A228855 Ivan Neretin, <a href="/A228855/b228855.txt">Table of n, a(n) for n = 1..10000</a>
%e A228855 Taking the first generation of edges of the tree to be G(1) = {(2,3)}, the edge (2,3) grows G(2) = {(3,5), (3,8)}, which grows G(3) = {(5,8), (5,13), (8,11),(8,19)}, ... Expelling duplicate nodes and sorting leave {2,3,5,8,11,13,...}.
%t A228855 f[x_, y_] := {{y, x + y}, {y, x + 2 y}}; x = 2; y = 3; t = {{x, y}};
%t A228855 u = Table[t = Flatten[Map[Apply[f, #] &, t], 1], {12}]; v = Flatten[u];
%t A228855 w = Flatten[Prepend[Table[v[[2 k]], {k, 1, Length[v]/2}], {x, y}]];
%t A228855 Sort[Union[w]]
%Y A228855 Cf. A141832, A228853, A228854, A228856.
%K A228855 nonn,easy
%O A228855 1,1
%A A228855 _Clark Kimberling_, Sep 05 2013