https://en.wikipedia.org/wiki/Pascal%27s_triangle

pascalsTriangle.py

def pascalsTriangle(n):
	triangle = [[1]]

	for i in xrange(1, n):
		row = []

		for j in xrange(len(triangle[i-1]) + 1):
			if j-1 >= 0 and j < len(triangle[i-1]):
				row.append(triangle[i-1][j-1] + triangle[i-1][j])

			elif j < len(triangle[i-1]):
				row.append(triangle[i-1][j])

			else:
				row.append(triangle[i-1][j-1])

		triangle.append(row)
	return triangle

print pascalsTriangle(6) # print rows 0-5 of Pascal's triangle