f_0(α)=α
f_β+1(α)=f_β(α)[f_β+1(α)]

f_0(ε_0)=ε_0
f_1(ε_0)=ω↑↑ω↑↑ω↑↑・・・=ω↑↑↑ω=ε_ω
f_2(ε_0)=φ(2,0)　?
f_β(ε_0)=φ(β,0)　?

f_ω(ε_0)=φ(ω,0)　?