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A028739 Nonsquares mod 26. 1
2, 5, 6, 7, 8, 11, 15, 18, 19, 20, 21, 24 (list; graph; refs; listen; history; text; internal format)
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

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Last modified April 12 17:17 EDT 2021. Contains 342929 sequences. (Running on oeis4.)