Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
%I #13 Aug 22 2020 17:43:20
%S 3,5,9,11,13,15,19,21,25,27,29,33,35,37,39,43,45,51,53,55,57,59,61,63,
%T 65,67,69,75,77,81,83,85,87,91,93,95,99,101,105,107,109,111,115,117,
%U 121,123,125,129,131,133,135,139,141,143,145,147,149,153,155,157,159,163
%N Odd numbers k such that x^2 == 2 (mod k) has no solution.
%C Complement of A058529 over the odd numbers: odd numbers k such that x^2 == 2 (mod k) has solutions.
%C Odd numbers k such that at least one prime factor of k is congruent to 3 or 5 modulo 8 (at least one prime factor is in A003629).
%C Also odd terms in A025020.
%H Robert Israel, <a href="/A329095/b329095.txt">Table of n, a(n) for n = 1..10000</a>
%e x^2 == 2 (mod 45) has no solution, so 45 is a term.
%p filter:= proc(t) (numtheory:-factorset(t) mod 8) intersect {3,5} <> {} end proc:
%p select(filter, [seq(i,i=1..1000,2)]); # _Robert Israel_, Nov 05 2019
%t Reap[Do[If[AnyTrue[FactorInteger[k][[All, 1]], MatchQ[Mod[#, 8], 3|5]&], Sow[k]], {k, 1, 999, 2}]][[2, 1]] (* _Jean-François Alcover_, Aug 22 2020 *)
%o (PARI) isA329095(k) = (k%2) && !issquare(Mod(2,k))
%Y Cf. A003629. A047621 is a subsequence.
%Y Cf. A058529, A057126, A025020 (numbers k such that x^2 == 2 (mod k) has no solution).
%K nonn,easy
%O 1,1
%A _Jianing Song_, Nov 04 2019