User blog comment:King2218/FGH Things/@comment-5029411-20140305213454

f[w]^[1](w) = f[w]^{f[w]^{...}(w)}(w)

f[w]^{1[1]}(w) = f[w]^{[1]}[w](w)

f[w]^[2](w) = f[w]^{f[w]^{...[1]}(w)[1]}(w)

f[w]^{[0][1]}(w) = f[w]^{[f[w]^{[...]}(w)]}(w)

fifth hierarchy ordinal is f[w]^[w]...[w]^[w](w)