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 A198589 #10 Mar 30 2012 17:23:02
%S A198589 7,15,29,61,117,241,245,267,469,483,497,535,537,965,981,985,995,1069,
%T A198589 1073,1075,1877,1933,1969,1971,1989,2009,2141,2147,2149,3861,3925,
%U A198589 3939,3941,3981,4017,4019,4043,4277,4293,4297,4301,7509,7733,7877,7885,7957,8035
%N A198589 Odd numbers producing 6 odd numbers in the Collatz iteration.
%H A198589 Vincenzo Librandi and T. D. Noe, <a href="/A198589/b198589.txt">Table of n, a(n) for n = 1..1000</a> (terms 1 to 282 from Vincenzo Librandi)
%t A198589 Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; t = {}; Do[If[Length[Select[Collatz[n], OddQ]] == 6, AppendTo[t, n]], {n, 1, 10000, 2}]; t
%Y A198589 Cf. A198584.
%K A198589 nonn
%O A198589 1,1
%A A198589 _T. D. Noe_, Oct 31 2011