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%I #10 Dec 14 2019 08:16:04
%S 3,5,6,10,12,13
%N Nonsquares mod 14.
%e Since 6 is not a perfect square and there are no solutions to x^2 = 6 mod 14 in integers, 6 is in the sequence.
%e Although 7 is not a perfect square either, there are solutions to x^2 = 7 mod 14, namely odd multiples of 7. Thus 7 is not in the sequence.
%t Complement[Range[0, 13], PowerMod[Range[14], 2, 14]] (* _Alonso del Arte_, Dec 14 2019 *)
%o (Scala) (0 to 13).diff((1 to 14).map(n => (n * n) % 14)) // _Alonso del Arte_, Dec 14 2019
%Y Cf. A010377.
%K nonn,fini,full
%O 1,1
%A _N. J. A. Sloane_
%E Incorrect term 7 removed by _Alonso del Arte_, Dec 14 2019