There are some coins that do something like this, primecoin's proof of work has to do with primes.

> The innovative prime proof-of-work in Primecoin not only provides security and minting to the network, but also generates a special form of prime number chains of interest to mathematical research. Thus primecoin network is energy-multiuse, compared to bitcoin.

This is of course very basic, but still, it's interesting.

http://primecoin.io/