Polyels
What are Polyels?
Polyels are polyforms made by connecting L-pipes end to end (not perpendicularly)
An analogy made by a mathematician I am working with, Pontus von Brömssen, is that polyels are like polyominoes, but instead of connecting squares, you are connecting squares with two chipped edges, which you cannot connect to. My analogy is that they are like polyaboloes that cannot connect at diagonals.
Enumeration
The sequence goes: 1, 2, 3, 6, 7, 12, 18.