Q: How many mathematicians does it take to screw in a lightbulb?

A: Just one, once you've managed to present the problem in terms he/she
is familiar with.

In earlier work, Wiener [1] has shown that one mathematician
can change a light bulb.

If k mathematicians can change a light bulb, and if one more simply
watches them do it, then k+1 mathematicians will have changed the
light bulb.

Therefore, by induction, for all n in the positive integers,
n mathematicians can change a light bulb.