（3+1）（3平方+1）（3的4方+1）（3的8方+1）（3的16方+1）-1
=[4/(3^2-1)]*(3^2-1)(3^2+1)(3^4+1)(3^8+1)(3^16+1)-1
=(1/2)*(3^4-1)(3^4+1)(3^8+1)(3^16+1)-1
=(1/2)(3^8-1)(3^8+1)(3^16+1)-1
=(1/2)(3^16-1)(3^16+1)-1
=(1/2)(3^32-1)-1
=(3^32)/2-3/2
=3(3^31-1)/2