Slides.txt contains some slides explaining counter machines and the busy beaver problem.
CounterMachines.txt contains the text of the code that can be copied into https://sagecell.sagemath.org/
By downloading PartSolutions.html and opening it in a browser, you can see solutions to some of the challenges posed. The BB_17 program is a Busy Beaver solution that runs for 17,433,922,066 steps! So if you run it, make sure you turn off the option of printing at every step.