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 A102643 #10 Aug 01 2017 02:52:44
%S A102643 3,5,11,17,17,13,43,257,257,41,683,4099,2731,2731,331,65537,65537,
%T A102643 262147,174763,174763,61681,199729,2796203,2796203,4051,9586981,87211,
%U A102643 15790321,15790321,1073741827,715827883,715827883,6700417,26317,86171
%N A102643 A006530(x)=2 is a local minimum if x=2^n. Running upward with argument x, the largest prime divisor should increase. The value of first peak is a(n).
%C A102643 We may call these terms "upward-zenith-primes" belonging to 2^n-s. They do not exceed next-primes after 2^n [A014210(n)].
%H A102643 Michael De Vlieger, <a href="/A102643/b102643.txt">Table of n, a(n) for n = 1..150</a>
%e A102643 n=22: 2^22=4194304; largest prime divisors for n+j, j=0, 1, 2, ... are {2, 2113, 5419, 16981, 61681, 199729, 7109}. The first peak after 2^22=4194304 is a(22)=199729.
%t A102643 Table[2 + Total@ TakeWhile[Differences@ Array[FactorInteger[#][[-1, 1]] &, 20, 2^n], # > 0 &], {n, 35}] (* _Michael De Vlieger_, Jul 31 2017 *)
%Y A102643 Cf. A006530, A102640, A102641, A102642, A102644, A014210.
%K A102643 nonn
%O A102643 1,1
%A A102643 _Labos Elemer_, Jan 21 2005