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 A242750 #15 May 22 2014 10:52:25
%S A242750 1,2,3,6,7,10,11,13,15,18,24,26,28,33,39,41,44,45,48,50,54,55,56,58,
%T A242750 62,65,68,69,71,75,79,83,85,93,95,107,108,109,110,117,118,119,120,123,
%U A242750 126,129,130,131,133,139,142,143,145,148,157,158,160,163,164,166,170,172,173,174,179,182,186,190,191,195
%N A242750 Positive integers n with property that n is a primitive root modulo prime(n).
%C A242750 According to the conjecture in A242748, this sequence should have infinitely many terms.
%H A242750 Zhi-Wei Sun, <a href="/A242750/b242750.txt">Table of n, a(n) for n = 1..10000</a>
%e A242750 6 is a member since 6 is a primitive root modulo prime(6) = 13, but 4 and 5 are not since 4 is not a primitive root modulo prime(4) = 7 and 5 is not a primitive root modulo prime(5) = 11.
%t A242750 dv[n_]:=Divisors[n]
%t A242750 n=0;Do[Do[If[Mod[k^(Part[dv[Prime[k]-1],j]),Prime[k]]==1,Goto[aa]],{j,1,Length[dv[Prime[k]-1]]-1}];n=n+1;Print[n," ",k];Label[aa];Continue,{k,1,195}]
%Y A242750 Cf. A000040, A000720, A242748, A242752.
%K A242750 nonn
%O A242750 1,2
%A A242750 _Zhi-Wei Sun_, May 21 2014