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 A040148 #11 Jul 08 2025 22:52:13
%S A040148 3,7,13,17,23,37,41,43,47,53,67,73,83,89,97,101,103,107,109,113,127,
%T A040148 137,149,157,163,167,173,181,193,197,223,227,233,241,257,263,269,277,
%U A040148 281,283,293,307,313,317,337,347
%N A040148 Primes p such that x^4 = 20 has no solution mod p.
%C A040148 Complement of A040147 relative to A000040. - _Vincenzo Librandi_, Sep 18 2012
%H A040148 Vincenzo Librandi, <a href="/A040148/b040148.txt">Table of n, a(n) for n = 1..1000</a>
%t A040148 ok[p_]:= Reduce[Mod[x^4 - 20, p] == 0, x, Integers] == False; Select[Prime[Range[100]], ok] (* _Vincenzo Librandi_, Sep 18 2012 *)
%o A040148 (Magma) [p: p in PrimesUpTo(500) | not exists{x : x in ResidueClassRing(p) | x^4 eq 20} ]; // _Vincenzo Librandi_, Sep 18 2012
%K A040148 nonn,easy
%O A040148 1,1
%A A040148 _N. J. A. Sloane_