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 A075485 #12 Dec 15 2023 08:01:04
%S A075485 1,8,17,18,107,108,47,48,62,63,157,158,159,160,130,131,225,226,178,
%T A075485 179,304,305,474,475,445,446,385,386,449,450,451,452,528,529,530,531,
%U A075485 532,533,534,535,536,537,587,588,589,590,591,592,593,594,595,596,853,854
%N A075485 Length of iteration list when Collatz-function is iterated with initial value 2^n - 1.
%C A075485 Somewhat surprisingly, these iterations take almost twice as long as the iterations for 2^n + 1. See A075486. - _T. D. Noe_, Jan 17 2013
%H A075485 T. D. Noe, <a href="/A075485/b075485.txt">Table of n, a(n) for n = 1..10000</a>
%H A075485 <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a>
%F A075485 a(n) = A008908(2^n-1).
%e A075485 n=4, 2^n - 1 = 15, list = {15, 46, 23, 70, 35, 106, 53, 160, 80, 40, 20, 10, 5, 16, 8, 4, 2, 1}, so a(4) = 18.
%t A075485 Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; Table[Length[Collatz[2^n - 1]], {n, 100}] (* _T. D. Noe_, Jan 17 2013 *)
%Y A075485 Cf. A006370, A008908, A074472, A075484, A075486, A075487, A075488.
%K A075485 nonn
%O A075485 1,2
%A A075485 _Labos Elemer_, Sep 26 2002