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 A191285 #12 Nov 17 2016 10:38:08
%S A191285 0,1,3,4,8,9,12,24,27,32,36,40,72,81,96,108,120,216,243,288,324,360,
%T A191285 364,512,648,729,800,864,972,1080,1092,1536,1944,2187,2400,2592,2916,
%U A191285 3240,3276,3280,4608,5832,6561,7200,7776,8748,9720,9828,9840,13824,17496,19683,21600,23328,26244,29160,29484,29520,29524
%N A191285 Increasing sequence S generated by these rules: 1 is in S, and if x is in S then 3x and floor((x^2)/2) are in S.
%C A191285 See A191203.
%H A191285 Ivan Neretin, <a href="/A191285/b191285.txt">Table of n, a(n) for n = 1..10000</a>
%e A191285 1 -> 0,3 -> 4,8,9,27 ->
%t A191285 g=12; Union[Flatten[NestList[{3#,Floor[(#^2)/2]}&,1,g]]]
%t A191285 (* A191285; use g>11 to get all of first 60 terms *)
%Y A191285 Cf. A191203.
%K A191285 nonn
%O A191285 1,3
%A A191285 _Clark Kimberling_, May 29 2011