x = (1+2)(1+2^2)(1+2^4)(1+2^8)...(1+2^256)
= -(1-2)(1+2)(1+2^2)(1+2^4)(1+2^8)...(1+2^256)
= -(1-2^2)(1+2^2)(1+2^4)(1+2^8)...(1+2^256)
= -(1-2^4)(1+2^4)(1+2^8)...(1+2^256)
= -(1-2^8)(1+2^8)...(1+2^256)
= -(1-2^16)...(1+2^256)
...
= -(1-2^256)(1+2^256)
= 2^512-1.
于是x+1 = 2^512是一个整数(2^256)的平方.