(2+1)(4+1)(16+1)(256+1)
=(2-1)(2+1)(4+1)(16+1)(256+1)
=(2^2-1)(2^2+1)(2^4+1)(2^8+1)
=(2^4-1)(2^4+1)(2^8+1)
=(2^8-1)(2^8+1)
=2^16-1
(2+1)(4+1)(16+1)(256+1)
=(2-1)(2+1)(4+1)(16+1)(256+1)
=(2^2-1)(2^2+1)(2^4+1)(2^8+1)
=(2^4-1)(2^4+1)(2^8+1)
=(2^8-1)(2^8+1)
=2^16-1