[ijyqkgnz] Expressing arbitrary numbers in chained arrow notation

Conway's chained arrow notation, while very powerful, can compactly express only a very limited set of numbers.

Tweak the notation a bit, sacrificing some compactness, to expand the set of numbers easily expressible.  I think we want to denote things like "add 6" at some specified point in the recursion.

Then, scientific notation could do 3.14 * 10 -> X -> Y -> Z...