%I #10 May 21 2014 20:58:16

%S 0,0,0,0,0,62264,4046803256,16382350221535464479,

%T 339840244399005511779394711120340266111

%N a(n) is the largest 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, A242619.

%K nonn

%O 0,6

%A _Arkadiusz Wesolowski_, May 19 2014