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 A143812 #11 Jun 05 2020 16:14:39
%S A143812 1,2,8,8,8,9,17,17,20,20,20,20,20,20,20,20,20,21,21,21,21,21,21,21,24,
%T A143812 24,112,112,112,112,112,112,112,112,112,112,112,112,112,112,112,112,
%U A143812 112,112,112,112,112,112,112,112,112,112,112,113,113,113,113,113
%N A143812 Maximal number of halving and tripling steps to reach 1 in '3x+1' problem for range (1, ..., n).
%H A143812 <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a>
%t A143812 nst[n_]:=Length[NestWhileList[If[EvenQ[#],#/2,3#+1]&,n,#>1&]]; nn=60; With[ {stps= Array[nst,nn]},Table[Max[Take[stps,n]],{n,nn}]] (* _Harvey P. Dale_, Apr 17 2014 *)
%Y A143812 Cf. A006877, A033492.
%K A143812 nonn
%O A143812 1,2
%A A143812 Benjamin Frost (benjamin.frost(AT)students.adelaide.edu.au), Sep 02 2008
%E A143812 Corrected and extended by _Harvey P. Dale_, Apr 17 2014