原式
=(3+1)(3^2+1)(3^4+1)(3^8+1)-3^16
=(1/2)(3-1)(3+1)(3^2+1)(3^4+1)(3^8+1)-3^16
=(1/2)(3^2-1)(3^2+1)(3^4+1)(3^8+1)-3^16
=..
=(1/2)(3^16-1)-3^16
=-3^16*(1/2)-(1/2)
(3+1)(3^2+1)(3^4+1)(3^8+1)-3^16
=[(3+1)(3-1)(3^2+1)(3^4+1)(3^8+1)]/(3-1)-3^16
=(3^2-1)(3^2+1))(3^4+1)(3^8+1)]/(3-1)-3^16
=(3^4-1)(3^4+1)(3^8+1)]/(3-1)-3^16
=(3^16-1)/2-3^16
=(-1-3^16)/2