A236959 Number of nonzero cubic residues modulo the n-th prime.

1, 2, 4, 2, 10, 4, 16, 6, 22, 28, 10, 12, 40, 14, 46, 52, 58, 20, 22, 70, 24, 26, 82, 88, 32, 100, 34, 106, 36, 112, 42, 130, 136, 46, 148, 50, 52, 54, 166, 172, 178, 60, 190, 64, 196, 66, 70, 74, 226, 76, 232, 238, 80

Offset: 1

Author

Carmine Suriano, Apr 22 2014

Keywords

• nonn

Examples

			a(4) = 2 for residues of x^3 (mod 7 = prime(4)) are 1 and 6.
a(3) = 4 for residues of x^3 (mod 5 = prime(3)) are 1, 2, 3, 4.
		

Crossrefs

Cf. A130290, A000040.

Programs

Maple

seq((ithprime(n)-1)/gcd(3,ithprime(n)-1), n=1..80); # Ridouane Oudra, Mar 13 2025

Formula

If prime(n)-1 = 3k then a(n) = k otherwise a(n) = prime(n)-1.

a(n) = A006093(n)/gcd(A006093(n),3). - Ridouane Oudra, Mar 13 2025

Extensions

a(20) corrected by Ridouane Oudra, Mar 13 2025