Exercise 1.22 - notable for introducing 'print' and 'timeit' more than anything else
Consolidated code to be shared by multiple exercises
let's name it for what it is
Exercise 1.23 - speedup of ~2, and minor discrepancies...
some exercises on the probabilistic Fermat test for primality
Exercise 1.27 - exhaustive Fermat test to check for Carmichael numbers (rare composite numbers that 'fool' the Fermat test)