Oh right, there is this blog.
I kind of wish there were problem sets for this course every week.

Finding the closed form sort of confused me, but when I went to the TA hours yesterday and asked about it, I got some more understanding.
And what helped the most was figuring out you should unwind all the way down to your base case (skipping most of the steps inbetween of course) - that is when you can really see what is going on.
And after talking to some friends, it seems that hadn't seen this either.