User blog:Ikosarakt1/Coding strings as ordinals (for Friedman's n(k))

I found some nice idea about how to calculate n(k) less directly. Suppose there are ordinal hierarchy \(F_\alpha(n)\) (algorithm for evaluating it is unknown), and we have some strings which codes ordinals for this hierarchy:

So, plugging n-th letter gives ordinal w^(n-1).