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 A019353 #19 May 13 2024 00:07:03 %S A019353 2,5,17,29,53,89,101,113,137,149,173,197,233,257,269,281,293,317,353, %T A019353 389,401,449,461,509,521,557,569,593,617,641,653,677,701,773,797,809, %U A019353 821,857,881,929,941,953,977,1013,1049,1061,1097,1109,1193,1217,1229,1277,1301 %N A019353 Primes with primitive root 27. %C A019353 From _Jianing Song_, May 12 2024: (Start) %C A019353 Members of A019334 that are not congruent to 1 mod 3. Terms greater than 2 are congruent to 5 modulo 12. %C A019353 According to Artin's conjecture, the number of terms <= N is roughly ((3/5)*C)*PrimePi(N), where C is the Artin's constant = A005596, PrimePi = A000720. Compare: the number of terms of A001122 that are no greater than N is roughly C*PrimePi(N). (End) %H A019353 Vincenzo Librandi, <a href="/A019353/b019353.txt">Table of n, a(n) for n = 1..1000</a> %H A019353 Wikipedia, <a href="https://en.wikipedia.org/wiki/Artin%27s_conjecture_on_primitive_roots">Artin's conjecture on primitive roots</a> %H A019353 <a href="/index/Pri#primes_root">Index entries for primes by primitive root</a> %t A019353 pr=27; Select[Prime[Range[300]], MultiplicativeOrder[pr, # ] == #-1 &] %o A019353 (PARI) isA019353(n) = isprime(n) && (n!=3) && znorder(Mod(27,n)) == n-1 \\ _Jianing Song_, May 12 2024 %Y A019353 Cf. A019334, A005596, A000720, A323594. %K A019353 nonn %O A019353 1,1 %A A019353 _David W. Wilson_