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

Author

Arkadiusz Wesolowski, Sep 05 2013

Keywords

• nonn
• hard
• more

Comments

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

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

Links

• Wilfrid Keller, Fermat factoring status
• Eric Weisstein's World of Mathematics, Fermat Number

Crossrefs

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