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

1,1

Comments

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

Links

Table of n, a(n) for n=1..4.

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.

Sequence in context: A328353 A078989 A156121 * A211961 A144940 A211962

Adjacent sequences: A280001 A280002 A280003 * A280005 A280006 A280007

Keyword

nonn,hard,more,changed

Author

Arkadiusz Wesolowski, Feb 21 2017

Status

approved