But it seems misleading to me. The title implies that an odd number could be the sum of two, three, four or five primes, but two and four are excluded because they will generate an even number, so isn’t it really saying that it can be expressed as the sum of either three or five primes? Anyway, nice proof.
[Via Geek Press]
[Update a while later]
D’oh! As the commenter notes, I’d forgotten that two is prime, and unique in it being an even prime.