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 A225124 #10 Dec 02 2013 14:32:22
%S A225124 1,2,4,8,3,32,21,128,85,512,151,2048,1365,8192,5461,32768,14563,
%T A225124 131072,87381,524288,349525,2097152,932067,8388608,5592405,33554432,
%U A225124 22369621,134217728,26512143,536870912,357913941
%N A225124 a(n) = least number k such that 2^n is highest in Collatz(3x+1) trajectory of k.
%e A225124 a(4)=3 since 3 is the least number such that largest member of Collatz(3 x + 1) trajectory of 3 is 2^4 = 16.
%t A225124 Coll[n_]:=NestWhileList[If[EvenQ[#],#/2,3*#+1]&,n,#>1 &]; t={}; Do[i=1; While[Max[Coll[i]] != 2^n, i++]; AppendTo[t, i], {n,0,25}]; t
%o A225124 (Haskell)
%o A225124 a225124 = (+ 1) . fromJust . (`elemIndex` a025586_list) . a000079
%o A225124 -- _Reinhard Zumkeller_, Apr 30 2013
%Y A225124 Cf. A000079, A025586, A095381, A231610.
%K A225124 nonn
%O A225124 0,2
%A A225124 _Jayanta Basu_, Apr 29 2013