http://link.springer.com/article/10.1007%2Fs00220-007-0350-z
Abstract
We generalize the classical definition of zeta-regularization of an infinite product. The extension enjoys the same properties as the classical definition, and yields new infinite products. With this generalization we compute the product over all prime numbers answering a question of Ch. Soulé. The result is 4π2. This gives a new analytic proof, companion to Euler’s classical proof, that the set of prime numbers is infinite.
If you are interested in this kind of math, 1+2+3+4+.... Wikipedia.en is fun to read.
