
How many ways can be represented

, i.e.

. I would like to know if there is some elegant way to represent this. Let me show a little bit concrete...



but I think that these ways are not elegant like the maximum idea, but...


but this representation already uses

form in itself (it's recursive in some sense), although it can be extended to

, or

.
So, does anybody know some other representation, or to come up with something?
Спасибо.
