riecoin

The projects Primecoin and Riecoin are digital currencies that try to provide proof of work algorithms with (somewhat) scientific value.

The hope behind Riecoin is that some breakthrough may come about for finding prime sextuplets.

There is (was?) one called riecoin that searched for dense clusters of primes.

Why not use Primecoin or Riecoin algorithms?

(For some period of time I was the author and maintainer of mining software for riecoin.

We have a few ways to do this, partial hash collisions, finding large primes, finding prime constellations, calculating cuckoo cycles… The primes seem to be valuable, alas nobody cared about primecoin or riecoin.

Please learn from the project at riecoin.org Latest news: "Last week, Riecoin – a project that doubles as decentralized virtual currency and a distributed computing system - quietly broke the record for the largest prime number sextuplet.

There's one called "nexus" that finds sparse clusters of primes of longer length than the ones in riecoin but where there can be a slightly larger inter-prime gap.

“Useful” PoW never really took off (primecoin and riecoin were prime number discovery POW functions that did not sustain long term value).

In the case of the prime number coins (primecoin, riecoin, nexus, probably some others), it was marketing that doing the pow would, in some hand wavy way help "science".

There are three that try to find primes - Primecoin, Riecoin, and Nexus.

(I wrote the miner that's now used for Riecoin.) There have been attempts to do others but none that really work, because in part of the problem you cite.