Three people are asked to prove that all of the odd numbers are prime – a physicist, a mathematician and a programmer.

The physicist goes first: “3 is a prime, 5 is a prime, 7 is a prime, 9 is a … oops, experimental error, 11 is a prime …”.
Next the mathematician takes a crack at it: “3 is a prime, 5 is a prime, 7 is a prime, and the rest by induction”.
Finally it’s the programmer’s turn: “3 is a prime, 5 is a prime, 7 is a prime, 9 is a prime, 11 is a prime …”.