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 A183212 #8 May 25 2015 17:15:47
%S A183212 2,6,8,18,11,24,26,54,16,33,35,72,38,78,80,162,23,48,49,99,52,105,107,
%T A183212 216,56,114,116,234,119,240,242,486,34,69,71,144,73,147,148,297,77,
%U A183212 156,157,315,160,321,323,648,83,168,170,342
%N A183212 Second of two trees generated by floor[(3n-1)/2].
%C A183212 See the comments at A183211, which is the mate for this tree.
%H A183212 Ivan Neretin, <a href="/A183212/b183212.txt">Table of n, a(n) for n = 1..8192</a>
%e A183212 First four levels of the tree:
%e A183212 .......................2
%e A183212 .......................6
%e A183212 .............8...................18
%e A183212 ...........11..24.............26....54
%t A183212 a = {2, 6}; row = {a[[-1]]}; Do[a = Join[a, row = Flatten[{Quotient[3 # - 1, 2], 3 #} & /@ row]], {n, 5}]; a (* _Ivan Neretin_, May 25 2015 *)
%Y A183212 Cf. A183211.
%K A183212 nonn,tabf
%O A183212 1,1
%A A183212 _Clark Kimberling_, Dec 30 2010