mathematics_in_lean

The set theory game on the same site it also fun https://adam.math.hhu.de/ Another one is mathematics in lean https://leanprover-community.github.io/mathematics_in_lean/ It's a text book with many examples for you to try. There are sample solutions which if you get stuck (which I often do) you can take a peek for some help. I actually just grep the solution file -A1 , -A2 etc to peek at the solutions one line at a time Example problems and solutions https://github.com/leanprover-community/mathematics_in_lean

I enjoyed working through "Theorem Proving in Lean 4", although it doesn't go deep into the mathematics side of things. I intend to work through "Mathematics in Lean"[2] to get more detail on that, but I want to finish "Programming Language Foundations in Agda" first. [1]: https://lean-lang.org/theorem_proving_in_lean4/ [2]: https://github.com/leanprover-community/mathematics_in_lean Edit: Oh, also the "Natural Number Game" is a nice, short intro to the theorem proving that gets straight to the point: https://adam.math.hhu.de/