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 A040105 #16 Jul 08 2025 22:47:37
%S A040105 2,5,11,19,31,59,71,79,101,109,131,139,149,151,179,181,191,199,211,
%T A040105 239,251,269,271,311,331,359,379,389,401,409,419,431,439,449,461,479,
%U A040105 491,499,521,541,569,571,599,619
%N A040105 Primes p such that x^4 = 5 has a solution mod p.
%C A040105 Union of 2, 5, A122869 (primes congruent to 11 or 19 modulo 20), and primes p == 1 (mod 4) such that 5^((p-1)/4) == 1 (mod p). - _Jianing Song_, Jun 20 2025
%H A040105 Vincenzo Librandi, <a href="/A040105/b040105.txt">Table of n, a(n) for n = 1..1000</a>
%t A040105 ok [p_]:=Reduce[Mod[x^4- 5, p] == 0, x, Integers] =!= False; Select[Prime[Range[200]], ok] (* _Vincenzo Librandi_, Sep 11 2012 *)
%o A040105 (Magma) [p: p in PrimesUpTo(800) | exists(t){x : x in ResidueClassRing(p) | x^4 eq 5}]; // _Vincenzo Librandi_, Sep 11 2012
%o A040105 (PARI) isA040105(p) = isprime(p) && (p==2 || p==5 || p%20==11 || p%20==19 || (p%4==1 && Mod(5,p)^((p-1)/4) == 1)) \\ _Jianing Song_, Jun 20 2025
%Y A040105 Apart from 2 and 5, subsequence of A045468.
%Y A040105 A385192 (which itself contains A122869) is a proper subsequence.
%K A040105 nonn,easy
%O A040105 1,1
%A A040105 _N. J. A. Sloane_