def lah_gen():   # generator (triangel rows)
    yield [1]
    L, n = [0], 0
    while True:
        L.append(1)
        for k in range(n, 0, -1):
            L[k] = L[k]*(n+k)+L[k-1]
        yield L
        n += 1

def lah_triangle(len):   # triangle as a list of rows
    A = lah_gen()
    return [list(A.next()) for _ in range(len)]

lah_triangle(7)

show(graphs.DyckGraph())