>>37
Amateur mathematician detected. It is obvious that there is a bijection between the set of mxn integer matrices and (m*n)-tuples of integers. Now there is another bijection between the set of (m*n)-tuples of integers and the set of integers.
Denote this bijection f. Let v in the set of n-tuples. Define the (i+nk)-th (where 0<=i<n) digit of f(v) to be the k-th digit of the i-th component of v.