# Polyiamond Tri-Oddities

A polyiamond *tri-oddity*
is a figure with ternary symmetry formed by some number of copies of
a polyiamond that is not a multiple of three.
Torsten Sillke first studied them in 1996.
Here are the minimal known tri-oddities for polyiamonds of order
up to 6.
Impossible polyiamonds are shown in black.
Please write if you find a smaller solution or solve an unsolved case.

For heptiamonds (7-iamonds), see Heptiamond
Tri-Oddities.
For polyhexes, see Polyhex Tri-Oddities.

[ Moniamond
| Diamond
| Triamond
| Tetriamonds
| Pentiamonds
| Hexiamonds
| Mirror Symmetry
]

These figures have mirror symmetry as well as ternary symmetry.
### Horizontal

#### Holeless Variant

### Vertical

#### Holeless Variant

### Both

#### Holeless Variant

*Last revised 2021-12-02.*

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Polyform Curiosities

Col. George Sicherman
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