%I #9 Nov 27 2019 01:38:14
%S 2,3,5,6,8,11,12,14,15,17,18,20,21,23,24,26
%N Nonsquares mod 27.
%t Complement[Range[0, 26], PowerMod[Range[27], 2, 27]] (* _Alonso del Arte_, Nov 27 2019 *)
%o (Scala) val squaresMod27 = (0 to 26).map(n => n * n).map(_ % 27)
%o (0 to 26).diff(squaresMod27) // _Alonso del Arte_, Nov 27 2019
%Y Cf. A010389.
%K nonn,fini,full
%O 1,1
%A _N. J. A. Sloane_