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%I #17 Feb 26 2024 14:19:05
%S 0,1,4,7,9,10,13,16,19,22,25,28,31,34,36,37,40,43,46,49,52,55,58,61,
%T 63,64,67,70,73,76,79
%N Squares mod 81.
%t Union[PowerMod[Range[81], 2, 81]] (* _Alonso del Arte_, Dec 27 2019 *)
%o (Sage) [quadratic_residues(81)] # _Zerinvary Lajos_, May 28 2009
%o (Scala) (1 to 81).map(n => (n * n) % 81).toSet.toSeq.sorted // _Alonso del Arte_, Dec 27 2019
%Y Cf. A028794, A055047.
%K nonn,fini,full,easy
%O 1,3
%A _N. J. A. Sloane_