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 A323594 #34 Feb 16 2025 08:33:57 %S A323594 7,19,31,43,79,127,139,163,199,211,223,283,331,379,463,487,571,607, %T A323594 631,691,739,751,811,823,859,907,1039,1063,1087,1123,1231,1279,1291, %U A323594 1327,1423,1447,1459,1483,1567,1579,1627,1663,1699,1723,1747,1831,1951,1987,1999 %N A323594 Primes p such that 3 is a primitive root modulo p while 27 is not. %C A323594 Primes p such that 3 is a primitive root modulo p (i.e., p is in A019334) and that p == 1 (mod 3). %C A323594 According to Artin's conjecture, the number of terms <= N is roughly ((2/5)*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). %H A323594 Amiram Eldar, <a href="/A323594/b323594.txt">Table of n, a(n) for n = 1..10000</a> %H A323594 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ArtinsConstant.html">Artin's constant</a>. %H A323594 Wikipedia, <a href="https://en.wikipedia.org/wiki/Artin%27s_conjecture_on_primitive_roots">Artin's conjecture on primitive roots</a>. %o A323594 (PARI) forprime(p=5, 2000, if(znorder(Mod(3, p))==(p-1) && p%3==1, print1(p, ", "))) %Y A323594 Complement of A019353 with respect to A019334. %Y A323594 Cf. also A005596, A000720. %Y A323594 Primes p such that 3 is a primitive root modulo p and that p == 1 (mod q): this sequence (q=3), A323617 (q=5), A323628 (q=7). %K A323594 nonn %O A323594 1,1 %A A323594 _Jianing Song_, Aug 30 2019