A few issues:

• I still found the description a little confusing, I was squaring both odd and even, and also didn't realise that we wanted the even position rather than actual number. I'm partly to blame but I feel it could have been worded a little better.
• There are no tests, you have to just hit submit.
• On hitting submit and failing, it doesn't tell you what was being passed to it, it just says 'expected x, got x' which makes it hard to diagnose the problem.
  The issues are a shame because I found this to be quite interesting to do, great apart from those issues.