

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



