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 A198592 #8 Dec 10 2023 19:44:05
%S A198592 33,65,67,131,133,261,269,273,289,525,529,533,547,555,571,577,579,583,
%T A198592 633,635,1045,1059,1077,1093,1099,1111,1143,1155,1157,1167,1177,1267,
%U A198592 1271,1273,2101,2117,2123,2133,2161,2189,2199,2221,2285,2309,2317,2321,2333
%N A198592 Odd numbers producing 9 odd numbers in the Collatz iteration.
%H A198592 T. D. Noe, <a href="/A198592/b198592.txt">Table of n, a(n) for n = 1..1000</a>
%t A198592 Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; t = {}; Do[If[Length[Select[Collatz[n], OddQ]] == 9, AppendTo[t, n]], {n, 1, 10000, 2}]; t
%t A198592 col9Q[n_]:=Count[NestWhileList[If[EvenQ[#],#/2,3#+1]&,n,#!=1&],_?(OddQ[#]&)]==9; Select[ Range[1,2501,2],col9Q] (* _Harvey P. Dale_, Dec 10 2023 *)
%Y A198592 Cf. A198584.
%K A198592 nonn
%O A198592 1,1
%A A198592 _T. D. Noe_, Oct 31 2011