User blog comment:C7X/Supremum Method for Defining an OCF/@comment-35470197-20200114061905/@comment-30279966-20200114092031

Supposedly changing the second line to \(C_{n+1,\nu}(\alpha)=\{\gamma+\delta, \omega^\gamma, \psi_\gamma(\eta):\gamma,\delta,\eta \in C_{n,\nu}(\alpha)\land\eta<\alpha\}\) might work.