Twenty. One to hold the bulb, two to turn the ladder, and 17 to be on the guest list.
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Climb up a tree and act like a nut
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One. He gives it to six Californians, thereby reducing the problem to an earlier joke...
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.
Bibliography:
[1] Wiener, Matthew P., <11485@ucbvax>, Re: YALBJ, 1986
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None, because people who glow in the dark don't need light bulbs.
Note: Topical to the Chernobyl Reactor disaster of 1984.
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