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%I #12 Nov 29 2017 00:04:03
%S 0,1,1,0,1,0,0,5,1,116503103764643,0,604944512477,11131,39,7
%N Least odd k such that k*2^n + 1 is a prime factor of a Fermat number 2^(2^m) + 1 for some m, or 0 if no such value exists.
%C The sequence continues: a(15) = ?, 1, 17753925353, a(18) = ?, 1575, 13, 579, a(22) = ?
%H Fermat factoring status, <a href="http://www.prothsearch.com/fermat.html">Prime factors of Fermat numbers</a>
%H FermatSearch, <a href="http://www.fermatsearch.org/index.html">Home page</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/FermatNumber.html">Fermat Number</a>
%Y Cf. A019434, A007117.
%K nonn,hard
%O 0,8
%A _Arkadiusz Wesolowski_, Mar 05 2014
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