There's a version of this plugin in the official pelican-plugins repo:
https://github.com/getpelican/pelican-plugins/tree/master/render_math
The original version here and the other version in pelican-plugins have slowly diverged due to people submitting issues and pull requests only to one but not the other.
It would serve the community well to consolidate the two versions again and make sure that all issues/pull-requests will go to the same place in the future.