用简便方法计算（2+1）x（2X2+1）x（2的四次幂+1）x（2的八次幂+1）+1

利用平方差公式
(2+1)*(2^2+1)*(2^4+1)*(2^8+1)
=(2-1)(2+1)*(2^2+1)*(2^4+1)*(2^8+1)
=(2^2-1)*(2^2+1)*(2^4+1)*(2^8+1)
=(2^4-1)*(2^4+1)*(2^8+1)
=(2^8-1)*(2^8+1)
=2^16 -1
=65536-1
=65535