The OEIS is supported by the many generous donors to the OEIS Foundation.
%I #12 Mar 18 2013 18:57:51
%S 1,2,4,3,6,12,7,9,18,25,33,43,39,78,105,135,123,169,159,295,283,111,
%T 222,297,175,103,91,121,31,27,54,73,97,129,171,231,313,411,543,327,
%U 649,859,763,1017,1351,1215,703,937,871,1161,2223,3097,2631,3567,3175,4233
%N Least number k such that the difference between the number of halving and tripling steps in the Collatz (3x+1) iteration is n.
%C This is the first number in row n of A222599.
%H 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 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 Cf. A213678, A222599.
%K nonn
%O 0,2
%A _T. D. Noe_, Mar 04 2013