A028785 - OEIS

A028785

Nonsquares mod 72.

2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, 24, 26, 27, 29, 30, 31, 32, 33, 34, 35, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 50, 51, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 65, 66, 67, 68, 69, 70, 71

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..60.

EXAMPLE

x^2 = 27 mod 72 has no solutions, so 27 is in the sequence.

x^2 = 28 mod 72 has the following solutions: x = 10, x = 26, x = 46, x = 62. So 28 is not in the sequence.

MATHEMATICA

Complement[Range[71], PowerMod[Range[71], 2, 72]] (* Alonso del Arte, Jan 14 2017 *)

PROG

(Scala) (0 to 71).diff((1 to 72).map(n => (n * n) % 72)) // Alonso del Arte, Dec 24 2019

CROSSREFS

Cf. A010433.

Sequence in context: A028761 A028809 A337533 * A166546 A167759 A028812

Adjacent sequences: A028782 A028783 A028784 * A028786 A028787 A028788

KEYWORD

nonn,fini,full,easy

AUTHOR

N. J. A. Sloane

STATUS

approved