When Christian Goldbach sat down in 1742 to write to Leonhard Euler I very much doubt that he had any idea that the resulting correspondence would ensure him math legacy. Goldbach’s conjecture is one of the famous unsolved problems in mathematics today. I suspect that one of the main reasons for its fame is that it is easy to state, but apparently very hard. Just in case you haven’t come across the conjecture, here’s a statement of it. (This is not exactly how Goldbach phrased it; he thought of 1 as a prime number. But this is a modern equivalent).

I have also included some Python code to help build up a feel for the Sieve of Eratosthenes.