My faculty even allow people to attend its courses as a regular student for some money (not much, ~35 Big Macs).
But of course, you need to be close to a university with decent linear algebra lectures, have enough time and so on. That's harder.
But of course, you need to be close to a university with decent linear algebra lectures, have enough time and so on. That's harder.
So all you need is a university that provides natural sciences. I can't imagine such a university being hard to find.