User blog comment:TySkyo/TySkyo's Notation/@comment-28633611-20160805164518/@comment-28633611-20160805171228

I wasn't refering to an analogue of BB₂(n), but to a naive extension alla the FGH:

Rayo₀(n) = Rayo(n)

Rayo₁(n) = Rayo₀ⁿ(n)

Rayo₂(n) = Rayo₁ⁿ(n)

And so on.