Counting up from 1, and including only natural numbers, think of something interesting about each number.
1 is interesting because multiplying by it has no effect
2 is interesting because it's the only even prime
3 is interesting because it's the sum of the two numbers before it
Tell me something interesting about 4, then 5, etc. For a very loose interpretation of "interesting".
(This is sparked off by a proof that there are no uninteresting numbers)