> You have fifteen seconds. Using standard math notation, English words, or both, name a single whole number—not an infinity—on a blank index card. Be precise enough for any reasonable modern mathematician to determine exactly what number you’ve named, by consulting only your card and, if necessary, the published literature.

Lol, we used to do this with my (extremely nerdy) friends group in college when we 'inducted' new members! I never knew that it was from something, I just thought it was tradition. We had some great entries -- a circle of nines with no beginning and ending, a very good drawing of a wolf, many protest entries, somebody accidentally wrote 1^1^1^1^1^... before realizing their folly, etc. Great times.