polyEnum

Enumerate all the fixed polyominoes of size n tiles. Returns numpolys, the number of fixed polyominoes.
A polyomino is a plane geometric figure formed by joining one or more equal squares edge to edge. It is a polyform whose cells are squares.
https://en.wikipedia.org/wiki/Polyomino
Uses algorithm from https://www.sciencedirect.com/science/article/pii/0012365X81902375?via%3Dihub
Authors: Aaron T. Becker and Yitong Lu