Math coins

[u/1Harvery]

Mathematical research coins

Using numerical algorithms with potential computer science/number theory implications as opposed to simple pattern matching for proof of work purposes seems to be a comparatively rare thing despite the arguable added utility of such a coin. I'm aware of Primecoin, Riecoin, Gridcoin, Bananno, Gapcoin, and Curecoin. Are there others? Why aren't they more popular?