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 A165768 #16 Sep 28 2015 20:49:38 %S A165768 2,11,7,2,271,6733,41,11,2,3769453,77647,2,541,1394161003757,13806493, %T A165768 5,3,1778463179021,193,19,17377902756647509,398407,3,389,137,137867,3, %U A165768 3,160038737,739,4889866261929241,37,5,48109,3190436507 %N A165768 Smallest prime factor of the semiprime 2^A165767(n)-A165767(n). %C A165768 a(n)=2 whenever A165767(n) is even. %H A165768 Max Alekseyev, <a href="/A165768/b165768.txt">Table of n, a(n) for n = 1..39</a> %F A165768 a(n) = (2^A165767(n)-A165767(n))/A165769(n). %e A165768 17377902756647509 is in this sequence because it is the smallest prime factor of the semiprime 2^199-199. %K A165768 nonn %O A165768 1,1 %A A165768 _M. F. Hasler_, Oct 08 2009 %E A165768 More terms from _Max Alekseyev_, Dec 13 2011