User blog comment:Nayuta Ito/An attempt to well-define OCF as a number notation/@comment-32697988-20190425100551

>If A=ψ_n(0): Cough(A) = Ω_(n-1), where Ω_0=ω

n must be a krudinal since only crudinals can come after ψ_, but you cannot subtract one from a krudinal.