I've seen it before, but it was using Knuth's up-arrow notation [1], which I like because it generalizes easily. [1] https://en.wikipedia.org/wiki/Knuth's_up-a

I've seen it before, but it was using Knuth's up-arrow notation [1], which I like because it generalizes easily. [1] https://en.wikipedia.org/wiki/Knuth's_up-arrow_notation https://en.wikipedia.org/wiki/Knuth's_up-arrow_notation