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 A222600 #12 Mar 18 2013 18:57:51
%S A222600 1,2,4,3,6,12,7,9,18,25,33,43,39,78,105,135,123,169,159,295,283,111,
%T A222600 222,297,175,103,91,121,31,27,54,73,97,129,171,231,313,411,543,327,
%U A222600 649,859,763,1017,1351,1215,703,937,871,1161,2223,3097,2631,3567,3175,4233
%N A222600 Least number k such that the difference between the number of halving and tripling steps in the Collatz (3x+1) iteration is n.
%C A222600 This is the first number in row n of A222599.
%H A222600 T. D. Noe, <a href="/A222600/b222600.txt">Table of n, a(n) for n = 0..264</a> (searching until the Collatz sequence has a term greater than 2^63)
%t A222600 Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; nn = 50; t = Table[0, {nn}]; n = 0; While[Min[t] == 0, n++; c = Collatz[n]; e = Select[c, EvenQ]; diff = 2*Length[e] - Length[c]; If[diff < nn - 1 && t[[diff + 2]] == 0, t[[diff + 2]] = n]]; t
%Y A222600 Cf. A213678, A222599.
%K A222600 nonn
%O A222600 0,2
%A A222600 _T. D. Noe_, Mar 04 2013