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 A135728 #6 Mar 31 2012 13:48:24
%S A135728 0,1,3,5,9,17,33,65,129,153,321,1425,1601,1889,3393,4097,6929,8193,
%T A135728 10497,11025,18273,28161,74585,85265,149345,337761,558341,839429,
%U A135728 1022105,1467393,7932689,8612097,23911397,58882625,75567105,293056017
%N A135728 Record indices of A135727(n) = max{ A001281^k(n);k=0,1,2,3... } (3x-1 problem).
%C A135728 This gives indices n for which A135727(n) is larger than all preceding values of that sequence. As in A135727(n), we include the fixed point 0 in the domain of A001281. Obviously, many but not all entries are of the form 2^k+1 and not all of such numbers are in the sequence (e.g. 257, 1025, 2049 are missing). Is there a simple way of characterizing the exceptions?
%o A135728 (PARI) A135728(Nmax=10^4)=local(m=-1);for(n=0,Nmax,if(m+0<m=max(m,A135727(n)),print1(n",")))
%Y A135728 Cf. A001281, A037084, A039500-A039505, A135727-A135730. A006370, A006577.
%K A135728 nonn
%O A135728 1,3
%A A135728 _M. F. Hasler_, Nov 26 2007
%E A135728 a(19)-a(36) from _Donovan Johnson_, Nov 06 2010