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 A243628 #8 Mar 18 2023 16:10:11
%S A243628 185,187,191,541,545,551,557,561,563,575,607,1629,1635,1637,1655,1659,
%T A243628 1671,1677,1681,1683,1685,1687,1725,1755,1803,1821,1825,1833,2007,
%U A243628 2011,4885,4917,4929,4953,4963,4965,4979,5015,5017,5029,5041,5043,5045,5061,5077,5081,5091,5121
%N A243628 Odd numbers producing 30 even numbers in the Collatz iteration.
%C A243628 See row 30 of A199636.
%H A243628 Vincenzo Librandi, <a href="/A243628/b243628.txt">Table of n, a(n) for n = 1..697</a>
%t A243628 Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; t = {}; Do[If[Length[Select[Collatz[n], EvenQ]] == 30, AppendTo[t, n]], {n, 1, 100000, 2}]; t
%t A243628 on30Q[n_]:=Count[NestWhileList[If[EvenQ[#],#/2,3#+1]&,n,#!=1&],_?EvenQ] ==30; Select[Range[1,5131,2],on30Q] (* _Harvey P. Dale_, Mar 18 2023 *)
%Y A243628 Cf. A199636, A199817, A199818.
%K A243628 nonn,fini,less
%O A243628 1,1
%A A243628 _Vincenzo Librandi_, Jun 08 2014