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A028727
Nonsquares mod 14.
1
3, 5, 6, 10, 12, 13
OFFSET
1,1
EXAMPLE
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.
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.
MATHEMATICA
Complement[Range[0, 13], PowerMod[Range[14], 2, 14]] (* Alonso del Arte, Dec 14 2019 *)
PROG
(Scala) (0 to 13).diff((1 to 14).map(n => (n * n) % 14)) // Alonso del Arte, Dec 14 2019
CROSSREFS
Cf. A010377.
Sequence in context: A187126 A065873 A072282 * A257346 A047327 A028927
KEYWORD
nonn,fini,full
EXTENSIONS
Incorrect term 7 removed by Alonso del Arte, Dec 14 2019
STATUS
approved