1,1

Table of n, a(n) for n=1..20.

x^2 = 7 mod 41 has no solutions, so 7 is in the sequence.

x^2 = 8 mod 41 has the solutions x = 7 and x = 34. Hence 8 is not in the sequence.

Complement[Range[40], PowerMod[Range[41], 2, 41]] (* Alonso del Arte, Jan 12 2017 *)

Sequence in context: A115127 A258354 A292608 * A028795 A004780 A292046

Adjacent sequences: A028751 A028752 A028753 * A028755 A028756 A028757

nonn,fini,full

N. J. A. Sloane

approved