(2+1)(2²+1)(2∧4+1)……[2∧(2n)+1]
=(2-1)(2+1)(2²+1)(2∧4+1)……[2∧(2n)+1]
=(2²-1)(2²+1)(2^4+1)……[2^(2n)+1]
=(2^4-1)(2^4+1)……[2^(2n)+1]
……
=[2^(2n)-1][2^(2n)+1]
=2^(4n)-1