先乘(2-1)=1,结果不变
然后反复利用平方差公式
(2+1)(2^2+1)(2^4+1)...(2^32+1)+1
=(2-1)(2+1)(2^2+1)(2^4+1)...(2^32+1)+1
=(2^2-1)(2^2+1)(2^4+1）.（2^32+1)+1
=(2^4-1)(2^4+1)...(2^32+1)+1
=...
=(2^32-1)(2^32+1)+1
=2^64-1+1
=2^64