Sure there is math behind it, I was at a paper factory once, I asked them about the whole A0 and so forth sizing, I was told in prefect german and translated that originally they made 1M^2 sheet (alle) and they would them take those and cut them by halfs, so when an order came in, it would read Alle/2 Alle/4 a so forth since they would then say take this pile to A, A2 and A4 cutting station. Who knows, but that is what the Aschaffenburg guide tolde me back in 1998, been telling everyone that story since… :/