User blog comment:P進大好きbot/Elementary Large Number/@comment-11227630-20190604040637

I need long time to understand your explanation.

But it seems that the coding (of the pair of an ordinal and an "FS index": \(\langle\alpha,n\rangle\)) is not \(\text{Code}(\alpha)\cdot2^n\) but \((2\cdot\text{Code}(\alpha)+1)\cdot2^n\), similar to the pairing method used in Loader's number.