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 A019356 #19 Sep 23 2018 11:37:06
%S A019356 11,23,41,43,47,59,61,79,89,109,131,151,167,173,179,193,197,199,251,
%T A019356 263,281,293,307,317,349,383,419,421,433,439,449,457,491,503,521,523,
%U A019356 541,557,569,577,641,647,653,659,673,677,743,751,761,773,787,797,809,829,863,881
%N A019356 Primes with primitive root 30.
%H A019356 Vincenzo Librandi, <a href="/A019356/b019356.txt">Table of n, a(n) for n = 1..1000</a>
%H A019356 <a href="/index/Pri#primes_root">Index entries for primes by primitive root</a>
%t A019356 Select[Prime[Range[200]], MultiplicativeOrder[30, #] == # - 1 &]
%t A019356 Join[{11,23},Select[Prime[Range[200]],PrimitiveRoot[#,30]==30&]] (* _Harvey P. Dale_, Sep 23 2018 *)
%K A019356 nonn,easy
%O A019356 1,1
%A A019356 _David W. Wilson_