One theorem started it all

Book excerpt: Have you ever wondered what a mathematical language of trees would be like? Would you like to know how it is linked to homeomorphically irreducible trees, and the case n = 10? Perhaps you are more interested in some experimental theorems, like the theorem of sum forms? Or some famous numbers, like Euler's number and pi? How about some fun experimentation with the Collatz conjecture? Or maybe you are an odd one and want to see some possibly controversial, but not entirely pseudo-mathematical ideas? Should your answer to any of these questions be yes, then join this experimentally wonderful journey to mathematical truth!