def triangles():
    n = 1
    rst = [1]
    while n > 0:
        l = [1]
        if n == 1:
            yield l
        else:
            for i in range(n - 2):
                l.append(rst[i] + rst[i+1])
            l.append(1)
            rst = l
            yield l
        n += 1