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 A198587 #26 Jun 20 2025 02:46:37
%S A198587 17,35,69,75,141,151,277,301,565,605,1109,1137,1205,2261,2275,2417,
%T A198587 2421,4437,4549,4821,4835,4849,9045,9101,9669,9685,9699,17749,18197,
%U A198587 19285,19341,19397,19417,36181,36405,38677,38741,38797,38833,38835,70997,72789,72817
%N A198587 Odd numbers producing 4 odd numbers in the Collatz iteration.
%C A198587 Start with A385110. If k is in sequence then so is 4*k + 1. - _Ralf Stephan_, Jun 18 2025
%H A198587 Vincenzo Librandi and T. D. Noe, <a href="/A198587/b198587.txt">Table of n, a(n) for n = 1..287</a> (first 134 terms from Vincenzo Librandi)
%t A198587 Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; t = {}; Do[If[Length[Select[Collatz[n], OddQ]] == 4, AppendTo[t, n]], {n, 1, 100000, 2}]; t
%Y A198587 Cf. A198584, A385110.
%K A198587 nonn
%O A198587 1,1
%A A198587 _T. D. Noe_, Oct 31 2011