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 A216884 #11 Sep 08 2022 08:46:03
%S A216884 2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,
%T A216884 97,101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,
%U A216884 181,191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271
%N A216884 Primes p such that x^61 = 2 has a solution mod p.
%C A216884 Complement of A059230 relative to A000040.
%C A216884 Naturally this sequence is not the same as A000040. First disagreement at index 73: a(73)=373, A000040(73)=367. [_Bruno Berselli_, Sep 20 2012]
%H A216884 Vincenzo Librandi, <a href="/A216884/b216884.txt">Table of n, a(n) for n = 1..1000</a>
%t A216884 ok[p_] := Reduce[Mod[x^61 - 2, p] == 0, x, Integers] == True; Select[Prime[Range[150]], ok]
%o A216884 (Magma) [p: p in PrimesUpTo(500) | exists(t){x: x in ResidueClassRing(p) | x^61 eq 2}];
%K A216884 nonn,easy
%O A216884 1,1
%A A216884 _Vincenzo Librandi_, Sep 19 2012