For something to work as a proof of work, it needs to have a couple of properties that most @home projects don't have: There needs to be a quick way to verify

For something to work as a proof of work, it needs to have a couple of properties that most @home projects don't have: There needs to be a quick way to verify a correct solution. There needs to be a way to pre-estimate the difficulty of the problem. There should be a way to adjust said difficulty. Ideally, there shouldn't be a time/memory tradeoff.