A238798 Least odd k such that k*2^n + 1 is a prime factor of a Fermat number 2^(2^m) + 1 for some m, or 0 if no such value exists.

0, 1, 1, 0, 1, 0, 0, 5, 1, 116503103764643, 0, 604944512477, 11131, 39, 7

Offset

0,8

Comments

The sequence continues: a(15) = ?, 1, 17753925353, a(18) = ?, 1575, 13, 579, a(22) = ?

Links

Table of n, a(n) for n=0..14.

Fermat factoring status, Prime factors of Fermat numbers

FermatSearch, Home page

Eric Weisstein's World of Mathematics, Fermat Number

Crossrefs

Cf. A019434, A007117.

Sequence in context: A009826 A255855 A255858 * A112871 A249421 A359226

Adjacent sequences: A238795 A238796 A238797 * A238799 A238800 A238801

Keyword

nonn,hard

Author

Arkadiusz Wesolowski, Mar 05 2014

Status

approved