Archive of problems

You can find the problem set and the solutions of the μ-Games here:
Problem Set – Edition 1
Problem Set – Edition 2
Problem Set – Edition 3
Problem Set – Edition 4
Problem Set – Edition 5
Problem Set – Edition 6
Problem Set – Edition 7
Problem Set – Edition 8
Problem Set – Edition 9
Problem Set – Edition 10
Problem Set – Edition 11
Problem Set – Edition 12

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