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%I #14 Nov 27 2019 01:39:05
%S 2,5,6,7,8,11,15,18,19,20,21,24
%N Nonsquares mod 26.
%e Since 2 is not a perfect square and there are no solutions to x^2 = 2 mod 26, 2 is in the sequence.
%e Although 3 is not a perfect square either, there are solutions to x^2 = 3 mod 26, such as x = 9, x = 17, 3 is not in the sequence.
%t Complement[Range[0, 25], PowerMod[Range[0, 25], 2, 26]] (* _Alonso del Arte_, Nov 26 2019 *)
%o (Scala) val squaresMod26 = (0 to 25).map(n => n * n).map(_ % 26)
%o (0 to 25).diff(squaresMod26) // _Alonso del Arte_, Nov 26 2019
%Y Cf. A010388.
%K nonn,fini,full
%O 1,1
%A _N. J. A. Sloane_
%E Incorrect term 13 removed by _Alonso del Arte_, Nov 26 2019
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