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 A039500 #29 Mar 26 2022 13:11:38
%S A039500 1,2,3,4,6,8,11,12,15,16,22,24,29,30,32,39,43,44,48,53,57,58,59,60,64,
%T A039500 65,69,71,77,78,79,85,86,87,88,95,96,97,101,103,105,106,113,114,115,
%U A039500 116,118,120,127,128,129,130,135,137,138,141,142,145,151,154,155,156
%N A039500 Iterations of "k->k/2 if k is even, k->3k-1 if k is odd" (A001281) starting at these numbers reach 1.
%C A039500 It appears that lim_{n->oo} a(n)/n = 5/2. - _Benoit Cloitre_, Jan 29 2006
%C A039500 Equivalent to the Collatz ('3n+1') problem for negative integers. - _Dmitry Kamenetsky_, Jan 12 2017
%C A039500 There are 327679 terms in this sequence which are less than 1000000. Based on this, I would suggest that the limit of a(n)/n is more likely to be 3 than 5/2. This is also a natural guess; there are three known periodic orbits for this recurrence. - _David Speyer_, Mar 25 2022
%H A039500 Alois P. Heinz, <a href="/A039500/b039500.txt">Table of n, a(n) for n = 1..20000</a>
%t A039500 colln[n_]:= NestWhile[If[EvenQ[#], #/2, 3#-1] &, n, FreeQ[{1, 5, 17}, #] &]; Select[Range[156], colln[#] == 1 &] (* _Jayanta Basu_, Jun 06 2013 *)
%Y A039500 Positive integers not in A037084.
%Y A039500 Cf. A039501, A039502, A039503, A039504, A039505.
%K A039500 nonn,easy
%O A039500 1,2
%A A039500 _Christian G. Bower_, Feb 15 1999