Yeah, he got you pretty good there

He did indeed. One must be more careful in stating results; I should have said that

Theorem

n! is even for all integers n > 1

 

Oh and, this is for Dave's benefit, the proof was thought up in the old Maths Institute at Warwick before Ian Stewart showed us how to do maths humour properly in a magazine called Manifold. If there are any still lying around somewhere at Warwick they are worth reading. My favourite cartoon in that magazine had a picture like this

Just realised that you can get an anthology of Manifold in:

 

Seven Years of Manifold: 1968-80

Ian Stewart (Editor), John Jaworski (Editor)

Publisher: Shiva Pub, Nantwich

ISBN: 0906812070

My favourite cartoon in that magazine had a picture like this

 

I don't know what's worse - the fact that I found that very amusing, or the fact that I want to read more