User blog comment:Vel!/1+w/@comment-1605058-20141012123611

One thing I wanted to point out too is that, actually, (standard) FGH can be thought of not as a hierarchy, but rather a single function f(a,n), taking arguments from Ord x N and taking values in N. This is similar to how Veblen hierarchy, phi_a(b), can be thought of as a single two-argument function phi(a,b).