A336719 Largest odd prime p for which the order of 2 mod p is at most n.

3, 7, 7, 31, 31, 127, 127, 127, 127, 127, 127, 8191, 8191, 8191, 8191, 131071, 131071, 524287, 524287, 524287, 524287, 524287, 524287, 524287, 524287, 524287, 524287, 524287, 524287, 2147483647, 2147483647, 2147483647, 2147483647, 2147483647, 2147483647

Offset

2,1

Comments

a(1) is undefined.

Changing "at most n" to "equal to n" in the definition gives A097406.

The first term that is not a Mersenne prime (A000668) is 4432676798593.

For a version without duplicates, see A336720. For a list of all n where a(n) increases, see A336721.

Links

Jeppe Stig Nielsen, Table of n, a(n) for n = 2..251

Prog

(PARI) re=0; for(n=2, +oo, p=vecmax(factor(2^n-1)[, 1]); p>re&&re=p; print1(re, ", "))

Crossrefs

Cf. A000668, A005420, A014664, A097406, A336720, A336721.

Sequence in context: A077629 A184467 A004794 * A272981 A086839 A359322

Adjacent sequences: A336716 A336717 A336718 * A336720 A336721 A336722

Keyword

nonn

Author

Jeppe Stig Nielsen, Aug 01 2020

Status

approved