Mathematician and a light bulb

The funny joke for you!Let us enjoy the following joke:

How many mathematicians does it take to screw in a light bulb?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.