A polypon is a polyform consisting of a finite nonempty edge-connected union of cells from the triangular grid subdivided into triangles
with angles 
,
, and 
, illustrated above. Cells are joined along complete
sides, and holes are allowed. Pieces are identified under isometries
of this subdivided grid. The division into constituent triangles
is part of each piece.
The numbers of polypons with 
,
2, ... components are 1, 2, 2, 4, 4, 10, 13, 29, 47, ... (OEIS A057784),
the first few of which are illustrated above.
