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%I #18 Dec 28 2019 14:46:24
%S 0,1,4,8,9,16,25,28,32,36,44,49
%N Squares mod 56.
%t Union[PowerMod[Range[56], 2, 56]] (* _Alonso del Arte_, Dec 28 2019 *)
%o (Sage) [quadratic_residues(56)] # _Zerinvary Lajos_, May 24 2009
%o (Scala) (1 to 56).map(n => (n * n) % 56).toSet.toSeq.sorted // _Alonso del Arte_, Dec 28 2019
%Y Cf. A028769.
%K nonn,fini,full,easy
%O 1,3
%A _N. J. A. Sloane_