The main web page really consists of a number of puzzles or paradoxes for you to solve. Some of what is said there is correct, some not correct, and your job is to work out which is which. You might find it helpful to come back to these questions again later on when you have read the full set of notes.
Exercise.
Is the argument that the sum of the quadratic series exists and is less than 2 correct?
Exercise.
Is the argument that the sum of the harmonic
series
Exercise.
Manipulating the sum
Exercise.
What goes wrong with the argument concerning the
sum