Think you have some mathematical/computing skills? Put them to the test at Project Euler. A lot of problems are available for which you must write some computer code to solve, usually less than a hundred lines. My preferred language is Python.
Here’s an example problem:
If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23. Find the sum of all the multiples of 3 or 5 below 1000.