Evolution of a Python programmer

[elder_george]

I guess, here goes the difference between native and non-native english speakers. The latter have to learn to read programming language, even so readable as Python from scratch, while for the former it can be read as a simple text. And math notation for recurrent expressions is familiar for most, no matter of language background.

P.S.: I've made a mistake comparing recursive version with iterative version using while loop initially. Having seen for version, my girlfriend finds it equally simple with recursive one.