code: def pascal(n):
      
      errors.is_positive_integer(n)
      result = numpy.zeros((n, n))
  
      #fill the first row and column
      for i in range(0, n):
          result[i, 0] = 1
          result[0, i] = 1
      if n > 1:
          for i in range(1, n):
              for j in range(1, n):
                  result[i, j] = result[i-1, j] + result[i, j-1]
      return result
docs: Return Pascal matrix
  
      :param int n: size of the matrix
  
      .. doctest::
  
          >>> from spectrum import pascal
          >>> pascal(6)
          array([[   1.,    1.,    1.,    1.,    1.,    1.],
                 [   1.,    2.,    3.,    4.,    5.,    6.],
                 [   1.,    3.,    6.,   10.,   15.,   21.],
                 [   1.,    4.,   10.,   20.,   35.,   56.],
                 [   1.,    5.,   15.,   35.,   70.,  126.],
                 [   1.,    6.,   21.,   56.,  126.,  252.]])
  
      .. todo:: use the symmetric property to improve computational time if needed