(7+4) (7^2+4^2) (7^4+4^4) (7^8+4^8)
=[(7-4)(7+4) (7^2+4^2) (7^4+4^4) (7^8+4^8)]/3=(7^2-4^2)(7^2+4^2) (7^4+4^4) (7^8+4^8)]/3
=(7^4-3^4)(7^4+4^4) (7^8+4^8)]/3
=(7^16-4^16)/3
(7+4) (7^2+4^2) (7^4+4^4) (7^8+4^8)
=[(7-4)(7+4) (7^2+4^2) (7^4+4^4) (7^8+4^8)]/3=(7^2-4^2)(7^2+4^2) (7^4+4^4) (7^8+4^8)]/3
=(7^4-3^4)(7^4+4^4) (7^8+4^8)]/3
=(7^16-4^16)/3