Problem 1171. matrix of natural number

Given a number n, create an n-by-n matrix in which the integers from 1 to n^2 resides seially as shown in the examples below.

Examples:

 Input  n = 3
 Output a = [ 1 2 3
              4 5 6
              7 8 9 ]
 Input  n = 4
 Output a = [ 1     2     3     4
              5     6     7     8
              9    10    11    12
              13   14    15    16]