%I #20 Nov 27 2019 01:38:25
%S 0,1,3,4,9,10,12,13,14,16,17,22,23,25
%N Squares mod 26.
%t Union[PowerMod[Range[0, 25], 2, 26]] (* _Alonso del Arte_, Nov 26 2019 *)
%o (Sage) [quadratic_residues(26)] # _Zerinvary Lajos_, May 24 2009
%o (Scala) (0 to 25).map(n => n * n).map(_ % 26).toSet.toSeq.sorted // _Alonso del Arte_, Nov 26 2019
%Y Cf. A028739.
%K nonn,fini,full
%O 1,3
%A _N. J. A. Sloane_