[1] https://plus.maths.org/content/too-big-write-not-too-big-gra...
[2] https://en.wikipedia.org/wiki/Graham%27s_number?oldformat=tr...
[3] And here is the man himself describing it https://www.youtube.com/watch?v=GuigptwlVHo
I'd write it out, but this margin is too narrow.