A228845 Least m such that (2k+1)*2^m + 1 is a prime factor of the Fermat number 2^(2^n) + 1.

1, 2, 4, 8, 16, 7, 8, 9, 11, 11, 12, 13, 14

Offset

0,2

Comments

a(n) >= n + 2 for n >= 2.

a(n) = A228846(n) if 2^(2^n) + 1 is prime or semiprime.

Links

Table of n, a(n) for n=0..12.

Wilfrid Keller, Fermat factoring status

Eric Weisstein's World of Mathematics, Fermat Number

Crossrefs

Cf. A000215, A019434, A023394, A046052, A228846.

Sequence in context: A212638 A016018 A333492 * A228846 A070336 A348433

Adjacent sequences: A228842 A228843 A228844 * A228846 A228847 A228848

Keyword

nonn,hard,more

Author

Arkadiusz Wesolowski, Sep 05 2013

Status

approved