Archive of problems

You can find the problem set and the solutions of the first three editions of the μ-Games here:
Problem Set – First Edition
Problem Set – Second Edition
Problem Set – Third Edition

Do you like to practise more? Take a look a Project Euler. For example this problem:

Starting in the top left corner of a 2×2 grid, and only being able to move to the right and down, there are exactly 6 routes to the bottom right corner.

How many such routes are there through a n×n grid?

source: https://projecteuler.net/problem=15