A372801 - OEIS

A372801

Order of 16 modulo the n-th prime: least k such that prime(n) divides 16^k-1.

1, 1, 3, 5, 3, 2, 9, 11, 7, 5, 9, 5, 7, 23, 13, 29, 15, 33, 35, 9, 39, 41, 11, 12, 25, 51, 53, 9, 7, 7, 65, 17, 69, 37, 15, 13, 81, 83, 43, 89, 45, 95, 24, 49, 99, 105, 37, 113, 19, 29, 119, 6, 25, 4, 131, 67, 135, 23, 35, 47, 73, 51, 155, 39, 79, 15, 21, 173, 87, 22, 179

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

OFFSET

2,3

COMMENTS

a(n) is the period of the expansion of 1/prime(n) in hexadecimal.

LINKS

Jianing Song, Table of n, a(n) for n = 2..10000

FORMULA

a(n) = A014664(n)/gcd(4, A014664(n)) = A082654(n)/gcd(2, A082654(n)).

a(n) <= (prime(n) - 1)/2.

PROG

(PARI) a(n) = znorder(Mod(16, prime(n))).