I had never spotted that before, each term of the series is the integral of the previous. That is pleasing! The Pi thing feels now less of a coincidence than t

I had never spotted that before, each term of the series is the integral of the previous. That is pleasing! The Pi thing feels now less of a coincidence than the fact that exp is a power. That probably falls out of expanding the polynomials but it so ingrained as taken for granted that it is wonderous when you think about it.