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%I #29 Sep 08 2022 08:46:18
%S 14,120,290,320,95330,2167800
%N Numbers k such that 7*2^k + 1 is a prime factor of a Fermat number 2^(2^m) + 1 for some m.
%C 18233956 belongs to this sequence, but its position is currently unknown. - _Jeppe Stig Nielsen_, Oct 05 2020
%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>
%o (Magma) IsInteger := func<k | k eq Floor(k)>; [n: n in [1..320] | IsPrime(k) and IsInteger(Log(2, Modorder(2, k))) where k is 7*2^n+1];
%Y Subsequence of A032353.
%Y Cf. A000215, A050527, A057778, A201364, A204620, A226366, A280004.
%K nonn,hard,more
%O 1,1
%A _Arkadiusz Wesolowski_, Feb 21 2017
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