Fractal from pascal triangle writen in python (sage mathematics)

sage-pascal-matrix.py

def pascal_matrix(size=500, zp=3):
    '''
    Creates a matrix of size x size, whose entries are numbers in zp, such that
    entry M_{ij} is obtained recursively as in pascal triangle. Each diagonal on 
    the matrix corresponds to a row in Pascal's triangle.
    '''
    M = ones_matrix(size,size)
    for i in range(1, size):
        for j in range(1, size):
            M[i, j] = M[i - 1, j] + M[i, j - 1]
        
    for i in range(1, size):
        for j in range(1, size):
            M[i, j] = mod(M[i, j], p)
    
    return M

M = pascal_matrix()
matrix_plot(M)