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 A228896 #9 Sep 09 2013 11:39:41
%S A228896 2,3,5,7,9,12,16,17,19,23,25,26,29,31,34,39,41,43,45,46,50,55,57,59,
%T A228896 62,63,64,66,69,70,71,74,75,81,84,85,91,93,94,97,98,99,101,104,105,
%U A228896 107,109,111,112,116,117,119,121,127,131,133,139,140,143,147,148
%N A228896 Nodes of tree generated as follows: (3,2) is an edge, and if (x,y) is an edge, then (y,y+x) and (y,2y+x) are edges.
%C A228896 The tree has infinitely many branches which are essentially linear recurrence sequences (and infinitely many which are not).
%H A228896 Vincenzo Librandi, <a href="/A228896/b228896.txt">Table of n, a(n) for n = 1..1000</a>
%e A228896 Taking the first generation of edges to be G(1) = {(3,2)}, the edge (3,2) grows G(2) = {(2,5), (2,7)}, which grows G(3) = {(5,7), (5,12), (7,9), (7,16)}, ... Expelling duplicate nodes and sorting leave (2,3,5,7,9,12,...).
%t A228896 f[x_, y_] := {{y, x + y}, {y, x + 2 y}}; x = 3; y = 2; t = {{x, y}};
%t A228896 u = Table[t = Flatten[Map[Apply[f, #] &, t], 1], {12}]; v = Flatten[u];
%t A228896 w = Flatten[Prepend[Table[v[[2 k]], {k, 1, Length[v]/2}], {x, y}]];
%t A228896 Sort[Union[w]]
%Y A228896 Cf. A228856.
%K A228896 nonn,easy
%O A228896 1,1
%A A228896 _Clark Kimberling_, Sep 08 2013