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A372801
Order of 16 modulo the n-th prime: least k such that prime(n) divides 16^k-1.
5
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
OFFSET
2,3
COMMENTS
a(n) is the period of the expansion of 1/prime(n) in hexadecimal.
LINKS
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))).
CROSSREFS
Cf. A302141 (order of 16 mod 2n+1).
Sequence in context: A205009 A101778 A292570 * A161670 A135514 A251754
KEYWORD
nonn,easy
AUTHOR
Jianing Song, May 13 2024
STATUS
approved