You're looking at StableBuild's Deleted PyPI mirror - where we index all deleted packages from the Python package registry.

passagemath-combinat
10.4.20

This version was deleted from PyPI around 2024-11-09. Installing fails with:
$ pip3 install passagemath-combinat==10.4.20 ERROR: Could not find a version that satisfies the requirement passagemath-combinat==10.4.20