title: How do I compress a long string with few different characters into a short string with many different characters?
body: <p>I have a (~500 character) string that I'd like to make shorter. This string consists of only 13 different characters, so I think there should be a way to use more characters and make the string shorter.  I would like to use all the characters that can be used in a URL.  I tried treating the string as a number in base 13 and converting it into an integer, then converting that into a string with a larger base, but the intermediate number is too large.</p>