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 A198591 #7 Mar 30 2012 17:23:03
%S A198591 25,49,51,99,101,197,205,217,397,405,433,435,441,475,789,821,833,857,
%T A198591 867,869,875,883,951,953,955,1589,1621,1649,1667,1713,1715,1733,1741,
%U A198591 1751,1765,1785,1901,1907,1911,3157,3185,3285,3299,3333,3427,3429,3469,3477
%N A198591 Odd numbers producing 8 odd numbers in the Collatz iteration.
%H A198591 Vincenzo Librandi, <a href="/A198591/b198591.txt">Table of n, a(n) for n = 1..1938</a>
%t A198591 Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; t = {}; Do[If[Length[Select[Collatz[n], OddQ]] == 8, AppendTo[t, n]], {n, 1, 10000, 2}]; t
%Y A198591 Cf. A198584.
%K A198591 nonn
%O A198591 1,1
%A A198591 _T. D. Noe_, Oct 31 2011