4^32-1=(2^16+1)(2^16-1)
=(2^16+1)(2^8+1)(2^8-1)
=(2^16+1)(2^8+1)(2^4+1)(2^4-1)
=(2^16+1)(2^8+1)(2^4+1)(2^2+1)(2^2-1)
10-20之间的只有：2^4+1和2^4-1
即：15 17