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 A127887 #12 Aug 20 2017 10:55:22
%S A127887 9,18,27,28,31,33,36,37,39,41,43,47,49,50,54,55,56,57,59,62,63,65,66,
%T A127887 71,72,73,74,78,79,82,83,86,87,89,91,94,95,97,98,99,100,103,105,107,
%U A127887 108,109,110,111,112,114,115,118,119,121,123,124,125,126,129,130,131,132,133,134,135,137,139,142,143,144,145
%N A127887 Indices of nonzero terms of A127886.
%C A127887 These are the numbers for which allowing the choice of x/2 or 3x+1 in the "3x+1" iteration makes a difference in the minimal number of steps to reach 1.
%C A127887 Thus these are the n for which A006577(n) > A127885(n).
%H A127887 Antti Karttunen, <a href="/A127887/b127887.txt">Table of n, a(n) for n = 1..695</a> (computed from the b-files of A006577 and A127885)
%t A127887 Position[#, k_ /; k > 0][[All, 1]] &@ Table[Length@ NestWhileList[If[OddQ@ #, 3 # + 1, #/2] &, n, # > 1 &] - Length@ NestWhileList[Flatten[# /. {k_ /; OddQ@ k :> 3 k + 1, k_ /; EvenQ@ k :> {k/2, 3 k + 1}}] &, {n}, FreeQ[#, 1] &], {n, 126}] (* _Michael De Vlieger_, Aug 20 2017 *)
%Y A127887 Cf. A006577, A127885, A127886.
%K A127887 nonn
%O A127887 1,1
%A A127887 _David Applegate_ and _N. J. A. Sloane_, Feb 04 2007
%E A127887 More terms from _Antti Karttunen_, Aug 18 2017