User blog comment:Deedlit11/Ordinal Notations IV: Up to a weakly inaccessible cardinal/@comment-24509095-20140507175906/@comment-5529393-20140605083923

Ikosarakt1: $$\vartheta$$ is a unary function. It is $$\theta$$ that is the binary function.

FB100Z: Well, as I pointed out in my post the $$\psi$$ function at the level of weakly inaccessibles is more like the $$\vartheta$$ function than the original $$\psi$$. So we could use $$\vartheta$$, but I used \psi</math because that what Rathjen uses.