def triangles():

    s = []

    while True:

        if len(s) == 0:

            s.append(1)

        else:

            x = s

            s = [1]

            k = 0

            while k < len(x) - 1:

                s.append(x[k] + x[k + 1])

                k = k + 1

            s.append(1)

        yield s