def triangles():
    L = [[1],[1,1]]
    yield L[0]
    yield L[1]
    while True:
        L.append([1])
        for ele in range(len(L[-2]) - 1):
            L[-1].append(L[-2][ele] + L[-2][ele + 1])
        L[-1].append(1)
        yield L[-1]