Okay, here’s one I just made up:
Q: How many mathematicians does it take to change a lightbulb?
A: n mathematicians
And here’s one that I found that really shouldn’t have made me laugh out loud, but did:
A woman walks into a bar accompanied by a dog and a cow. The bartender
says, “Hey, no animals are allowed in here.”
The woman replies, “These are very special animals.”
“They’re knot theorists.”
The bartender raises his eyebrows and says, “I’ve met a number of
knot theorists who I thought were animals, but never an animal that
was a knot theorist.”
“Well, I’ll prove it to you. Ask them them anything you like.”
So the bartender asks the dog, “Name a knot invariant.”
“Arf, arf” barks the dog.
The bartender scowls and turns to the cow asking, “Name a topological
The cow says, “Mu, mu.”
At this point the bartender turns to the woman, says, “Just what are
you trying to pull” and throws them out of the bar.
Outside, the dog turns to the woman and asks, “Do you think I should
have said the Jones polynomial?”