A028739 Nonsquares mod 26.

2, 5, 6, 7, 8, 11, 15, 18, 19, 20, 21, 24

Offset

1,1

Links

Table of n, a(n) for n=1..12.

Example

Since 2 is not a perfect square and there are no solutions to x^2 = 2 mod 26, 2 is in the sequence.
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.

Mathematica

Complement[Range[0, 25], PowerMod[Range[0, 25], 2, 26]] (* Alonso del Arte, Nov 26 2019 *)

Prog

(Scala) val squaresMod26 = (0 to 25).map(n => n * n).map(_ % 26)
(0 to 25).diff(squaresMod26) // Alonso del Arte, Nov 26 2019

Crossrefs

Cf. A010388.

Sequence in context: A028791 A080727 A283974 * A074291 A134026 A220655

Adjacent sequences: A028736 A028737 A028738 * A028740 A028741 A028742

Keyword

nonn,fini,full

Author

N. J. A. Sloane

Extensions

Incorrect term 13 removed by Alonso del Arte, Nov 26 2019

Status

approved