 Knuth's up-arrow notation

Knuth's up-arrow notation is a way to represent very large numbers, especially those that arise in combinatorial mathematics and computer science. It was developed by Donald Knuth in 1976 as a method to describe exponential towers and hyperoperations. The basic idea revolves around using arrows to denote repeated operations. Let's break it down: 1. **Single Arrow**: The notation \( a \uparrow b \) is equivalent to \( a^b \) (i.e.