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%I #20 Dec 18 2019 21:51:53
%S 0,1,4,7,9,10,13,16
%N Squares mod 18.
%t Union[PowerMod[Range[18], 2, 18]] (* _Alonso del Arte_, Dec 18 2019 *)
%o (Sage) [quadratic_residues(18)] # _Zerinvary Lajos_, May 24 2009
%o (Scala) (1 to 18).map(n => (n * n) % 18).toSet.toSeq.sorted // _Alonso del Arte_, Dec 18 2019
%Y Row 18 of A096008.
%Y Cf. A028731.
%K nonn,fini,full
%O 1,3
%A _N. J. A. Sloane_