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 A302988 #14 Apr 06 2021 02:58:04 %S A302988 2,5,7,11,13,31,73,241,367,491,577,733,757,971,991,2593,2731,3307, %T A302988 3391,3529,4591,5113,7591,8011,8713,11131,17377,17911,18433,21757, %U A302988 24181,34651,36559,38921,39367,41141,52951,53593,55201,55681,59051,85933,93871,95791,102241,105031 %N A302988 Primes p such that p - 3 divides 3^p - 3. %C A302988 Conjecture: the sequence is infinite. %H A302988 Amiram Eldar, <a href="/A302988/b302988.txt">Table of n, a(n) for n = 1..10000</a> %t A302988 Select[Prime[Range[25]], Divisible[3^# - 3, # - 3] &] (* _Alonso del Arte_, Apr 17 2018 *) %t A302988 Select[Range[10^5], # != 3 && PrimeQ[#] && PowerMod[3, #, # - 3] == Mod[3, # - 3] &] (* _Amiram Eldar_, Apr 06 2021 *) %o A302988 (PARI) isok(p) = isprime(p) && (p != 3) && (Mod(3,p-3)^p == Mod(3,p-3)); \\ _Michel Marcus_, Apr 17 2018 %Y A302988 Cf. A000040, A000244, A302987. %K A302988 nonn %O A302988 1,1 %A A302988 _Alex Ratushnyak_, Apr 17 2018