Moment over an espresso

 I am at common grounds cafe right now. I had an espresso and today I taught few interesting things including Polya's way of deriving the sum of first n square numbers. I also jotted down my thoughts on bachet's conjecture (special case) which Polya does in his book. I am reading the insight where you can find the sum of any divisors by using previous divisors. At first it looks intimidating that how Euler came to think about such weird pattern of recursive way to derive the sequence but as you read on his insight about generating function makes it easy to follow. It sure is an interesting book.