(2+1)*(2^2+1)*(2^4+1)*...*(2^128+1)+1
=(2-1)(2+1)*(2^2+1)*(2^4+1)*...*(2^128+1)+1
=(2^1-1)(2^2+1)*(2^4+1)*...*(2^128+1)+1
=(2^4-1)(2^4+1)*...*(2^128+1)+1
=2^256-1+1
=2^256
(2+1)*(2^2+1)*(2^4+1)*...*(2^128+1)+1
=(2-1)(2+1)*(2^2+1)*(2^4+1)*...*(2^128+1)+1
=(2^1-1)(2^2+1)*(2^4+1)*...*(2^128+1)+1
=(2^4-1)(2^4+1)*...*(2^128+1)+1
=2^256-1+1
=2^256