Essential properties of a polyform set

When polyforms were invented, sets had to be constructed first. One of the most interesting questions was to find a function that gives the exact size of a set of n cells with a specific cell form. Later on, questions related to the shapes that can be formed with a set (using all pieces exactly once) were investigated: largest enclosed area, shortest perimeter and so on.

When computer solvers became easy to code and run, when computer power allowed a lot of calculation in little time, it became possible to look for shapes with the heighest number of solutions.

PropertyValue for trihexesValue for pentiamondsNotes
Type of cellshexagonstriangles
Number of cells per piece35
Number of pieces34
Symmetrical pieces32
Number of possible connected shapes951491 030A measure of a sets scope of shapes. A very heigh proportion are without esthetic or functional value, though.
Symmetrical connected shapes666Esthetically satisfying shapes -- polyform enthusiasts rarely construct assymetric shapes.
Connected shapes with holes1090,702Because of the geometry of the triangular grid, most of the holes share a summit with the edge of the shape itself. This is impossible with polyhexes but possible with squares.
Largest farm (fully enclosed hole)28The hole touches the edge of the shape via a single summit in the case of the pentiamonds.
Number of largest farms11
Most distinct holes in a shape13
Shapes with most holes108
Maximal number of solutions per shape44A measure of a set's combinatorial complexity.
Number of shapes with most solutions (Champion shapes)25
Minimal perimeter of a connected shape2212These are the most compact shapes that can be formed with the set.
Number of shapes with minimal perimeter17
Number of convex connected shapes01There are no convex shapes for polyhexes and only rectangles work with polyominoes. So this property is meaningful only for polyiamonds. There is just one convex pentiamond shape, for instance, as it has been proved by George Sicherman.
▽▲▽ POLYAMONDS, POLYHEXES AND OTHER POLYFORMS ▲▽▲

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