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 A183211 #8 May 25 2015 17:07:20
%S A183211 1,3,4,9,5,12,13,27,7,15,17,36,19,39,40,81,10,21,22,45,25,51,53,108,
%T A183211 28,57,58,117,59,120,121,243,14,30,31,63,32,66,67,135,37,75,76,153,79,
%U A183211 159,161,324,41,84,85,171,86,174,175,351,88,177
%N A183211 First of two trees generated by floor[(3n-1)/2].
%C A183211 This tree grows from (L(1),U(1))=(1,3). The second tree, A183212, grows from (L(2),U(2))=(2,6). Here, L(n)=floor[(3n-1)/2] and U(n)=3n. The two trees are complementary in the sense that every positive integer is in exactly one tree. The sequence formed by taking the terms of this tree in increasing order is A183213. Leftmost branch of this tree: A183207. Rightmost: A000244. See A183170 and A183171 for the two trees generated by the Beatty sequence of sqrt(2).
%H A183211 Ivan Neretin, <a href="/A183211/b183211.txt">Table of n, a(n) for n = 1..8192</a>
%F A183211 See the formula at A183209, but use L(n)=floor[(3n-1)/2] and U(n)=3n instead of L(n)=floor(3n/2) and U(n)=3n-1.
%e A183211 First four levels of the tree:
%e A183211 .......................1
%e A183211 .......................3
%e A183211 ..............4..................9
%e A183211 ............5...12............13....27
%t A183211 a = {1, 3}; row = {a[[-1]]}; Do[a = Join[a, row = Flatten[{Quotient[3 # - 1, 2], 3 #} & /@ row]], {n, 5}]; a (* _Ivan Neretin_, May 25 2015 *)
%Y A183211 Cf. A183170, A183212, A001651, A008585, A183209, A183213.
%K A183211 nonn
%O A183211 1,2
%A A183211 _Clark Kimberling_, Dec 30 2010