Graham's number - for a while, the largest number used in a proof: https://www.youtube.com/watch?v=XTeJ64KD5cg https://www.youtube.com/watch?v=XTeJ64KD5cg Ther

Graham's number - for a while, the largest number used in a proof: https://www.youtube.com/watch?v=XTeJ64KD5cg https://www.youtube.com/watch?v=XTeJ64KD5cg There are faster growing sequences as well, see: http://math.stackexchange.com/questions/2497/what-is-the-biggest-number-ever-used-in-a-mathematical-proof http://math.stackexchange.com/questions/2497/what-is-the-big... both fun as well. But busy beaver consumes them all.