def triangle(n):
    if n == 0:
        return []
    if n == 1:
        return [[1]]
    if n == 2:
        return [[1],[1,1]]
    if n > 2 :
        i = 0
        middle_nums = []
        while i < len(triangle(n-1))-1:
            temp = triangle(n-1)[n-2][i] + triangle(n-1)[n-2][i+1]
            middle_nums.append(temp)
            i = i + 1
        last_row = [1] + middle_nums + [1]
        return triangle(n-1) + [last_row]