%I #10 May 21 2014 20:57:29
%S 0,0,0,0,0,20449,1438793759,8479443857936402504,
%T 17340632172455487023654788790090010704
%N a(n) is the smallest number in the interval (1, 2^(2^(n-1))) that is a member of a pair of integers the sum of whose squares is equal to the Fermat number 2^(2^n) + 1, or 0 if no such number exists.
%C 2^(2^n) + 1 belongs to A019434 if and only if a(n) = 0.
%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Fermat_number">Fermat number</a>
%Y Cf. A000215, A242620.
%K nonn
%O 0,6
%A _Arkadiusz Wesolowski_, May 19 2014