Ah I see now that you have "until the nth year", maybe change that to [n]th year, with the n highlighted the same as the other variables, as these are what draws the eye. Fun kata though.

I had to re-read the explanation a few times to find out what 'n' meant. As compounding interest is the main theme of the kata, I think this could be made clearer.

Your comment says you use a hash, but you are just checking in the array every time. "table" is redundant :)

I also get this error, very annoying.

Python: Unknown error after 1700ms