Some parts of this library were copied from elsewhere on the internet.  When I
first started assembling this library, I had no ambitions of publication, and as
such, I wasn't terribly concerned with attribution; consequently, some of the
proper sourcing of the copied code is lost.  The sources I can recall are:

isqrt is largely unmodified from primo's post at
https://codegolf.stackexchange.com/a/9088.

siqs is derived from Stephan Kollman's repository at
https://github.com/skollmann/PyFactorise.

