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 A220139 #5 Jan 02 2013 18:49:24
%S A220139 1,2,16,52,160,9232,27700,83104,599056,1797172,5391520,38862808,
%T A220139 131161984,393485956,1180457872,3541373620,10624120864,87327950740,
%U A220139 261983852224,785951556676,2357854670032,7553654536192,22660963608580,67982890825744,203948672477236
%N A220139 The highest value of the Collatz iteration (3x+1) starting at a(n-1) + 1, with a(1) = 1.
%C A220139 The length of the trajectory of a(n) is A220140(n).
%H A220139 T. D. Noe, <a href="/A220139/b220139.txt">Table of n, a(n) for n = 1..500</a>
%e A220139 The Collatz trajectory of 2 + 1 is (3, 10, 5, 16, 8, 4, 2, 1). Hence, a(3) = 16. The trajectory of 16 + 1 is (17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1). Hence, a(4) = 52.
%t A220139 Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; c = {1}; t = {}; Do[AppendTo[t, Max[c]]; c = Collatz[t[[-1]] + 1], {30}]; t
%Y A220139 Cf. A070165 (trajectory of n).
%K A220139 nonn
%O A220139 1,2
%A A220139 _T. D. Noe_, Jan 02 2013