Solutions 15, 16, cleaned up 14

Just removed comments from fourteen.

I did a "cheater" solution for sixteen in Erlang, since it handles large
numbers with ease, but I also did a "harder" version without using
ridiculously large numbers.

I spent a few hours drawing doodles and noodling over fifteen before I
stumbled on the simple recursive solution. I had come up with a nifty
little equation for solving it but it turned out to be hopelessly naive.