In this new video from Numberphile, mathematician Alex Bellos explains a drawing by fellow mathematician Edmund Harris that gives the Collatz Conjecture a more impressionistic nature.

For each number in the tree – look at the 13, for example – the numbers along the branch leading downwards are those in its Collatz sequence.

The Collatz Conjecture, which is also known as the 3n+1 Problem, states that the sequence produced by every positive integer eventually reaches the number 1. This has been an open question since at ...