A242620 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.

0, 0, 0, 0, 0, 62264, 4046803256, 16382350221535464479, 339840244399005511779394711120340266111