User blog comment:Kyodaisuu/English description of Fish numbers/@comment-25418284-20131102173245/@comment-25418284-20131103185746

I understand it now. Part of it was me misunderstanding what f(a)=b means; I thought f was something that needed to be defined within the formula.

A FOST self-interpreter wouldn't be too hard. The catch is that Rayo's function can't use the self-interpreter because it creates a contradiction, which is where the oracle comes in.