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 A049558 #18 Jul 20 2025 07:23:23
%S A049558 2,7,17,23,31,41,47,71,73,89,97,103,113,127,137,151,167,191,193,199,
%T A049558 223,233,239,241,257,263,271,281,311,337,353,359,367,383,401,409,431,
%U A049558 433,439,449,457,463,479,487,503,569,577,593,601,607,617,631,641,647
%N A049558 Primes p such that x^26 = 2 has a solution mod p.
%C A049558 Complement of A059314 relative to A000040. - _Vincenzo Librandi_, Sep 14 2012
%H A049558 R. J. Mathar, <a href="/A049558/b049558.txt">Table of n, a(n) for n = 1..1000</a>
%H A049558 <a href="/index/Pri#smp">Index entries for related sequences</a>
%e A049558 0^26 == 2 (mod 2). 3^26 == 2 (mod 7). 7^26 == 2 (mod 17). 8^26 == 2 (mod 23). 2^26 == 2 (mod 31). 6^26 == 2 (mod 41). 21^26 == 2 (mod 47). 31^26 == 2 (mod 71). 36^26 == 2 (mod 73). 8^26 == 2 (mod 89). - _R. J. Mathar_, Jul 20 2025
%t A049558 ok[p_]:= Reduce[Mod[x^26 - 2, p] == 0, x, Integers] =!= False; Select[Prime[Range[150]], ok] (* _Vincenzo Librandi_, Sep 14 2012 *)
%o A049558 (Magma) [p: p in PrimesUpTo(700) | exists(t){x : x in ResidueClassRing(p) | x^26 eq 2}]; // _Vincenzo Librandi_, Sep 14 2012
%Y A049558 Cf. A000040, A059314.
%K A049558 nonn,easy
%O A049558 1,1
%A A049558 _N. J. A. Sloane_