Polyiamond

A polyiamond (also polyamond or simply iamond, or sometimes triangular polyomino[1]) is a polyform whose base form is an equilateral triangle. The word polyiamond is a back-formation from diamond, because this word is often used to describe the shape of a pair of equilateral triangles placed base to base, and the initial 'di-' looks like a Greek prefix meaning 'two-' (though diamond actually derives from Greek ἀδάμας - also the basis for the word "adamant"). The name was suggested by recreational mathematics writer Thomas H. O'Beirne in New Scientist 1961 number 1, page 164.

  1. ^ Sloane, N.J.A. (July 9, 2021). "A000577". OEIS. The OEIS Foundation Inc. Retrieved July 9, 2021. triangular polyominoes (or triangular polyforms, or polyiamonds)