OFFSET
1,1
COMMENTS
The corresponding primes are 3, 7, 3, 89, 31, 178481, 5, 7, 3, 23, 11, ...
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..64
EXAMPLE
5 is in the sequence since ord(2, 5) = 4 and (2^4 - 1)/5 = 3 is prime.
MATHEMATICA
aQ[n_] := PrimeQ[(2^MultiplicativeOrder[2, n] - 1)/n]; Select[Range[10000], aQ]
PROG
(PARI) is(n) = n%2 && isprime((2^znorder(Mod(2, n))-1)/n); \\ Amiram Eldar, Aug 26 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Dec 29 2017
STATUS
approved