A280004 - OEIS

A280004

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

%I #54 Jan 16 2023 08:07:49

%S 67,9431,461081,2543551

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

%H Proth Search Page, <a href="http://www.prothsearch.com/fermat.html">Prime factors of Fermat numbers</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/FermatNumber.html">Fermat Number</a>

%Y Subsequence of A002256.

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

%K nonn,hard,more

%O 1,1

%A _Arkadiusz Wesolowski_, Feb 21 2017