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.