A280004 Numbers k such that 9*2^k + 1 is a prime factor of a Fermat number 2^(2^m) + 1 for some m.

67, 9431, 461081, 2543551

Offset: 1

Author

Arkadiusz Wesolowski, Feb 21 2017

Keywords

• nonn
• hard
• more

Comments

Fernando (Remark 5.2) shows that all terms are odd. - Jeppe Stig Nielsen, Jan 02 2025

Links

• R. Fernando, Morehead-like restrictions on Fermat divisors.
• Proth Search Page, Prime factors of Fermat numbers
• Eric Weisstein's World of Mathematics, Fermat Number

Crossrefs

Subsequence of A002256.

Cf. A000215, A050528, A057778, A201364, A204620, A226366, A280003.