User blog comment:PsiCubed2/Help Me Understand Ordinals Beyond the BHO/@comment-30118230-20170220203230/@comment-30754445-20170307010524

It's helpful in the broad strokes, but I was really looking for the details of how everything works.

I'm also not very well versed in the ϑ function. I don't like how it jumps around (for example, skipping ζ₀ and going straight to ε(ζ₀+1) when going through the epsilon numbers), so I've never bothered to learn it in detail.