Firstly, we should distinguish m = {x | x = 2 n-2 m, n, m ∈ n, n >；; All possible elements in M and their laws can be considered as follows:

2 n-2 m = 2 m [2 (n-m)], the value of n-m can be 0, 1, 2,3, ..., and the value of m is also 1, 2,3, ..., so try from the smallest. If 19 12, then 2 n-2 m must be less than1912 (except 0 when n = m); If n is greater than or equal to 12 and 2 12 = 4096, then 2 n-2 m must be greater than 2048 (except 0 when n = m). Then the value of n is defined as 1 1, 21= 2048, then 2048-2 6 = 1986, 2048-2 7 = 1920, these two.