Number of triangular polyominoes (or triangular polyforms, or polyiamonds) with n cells (turning over is allowed, holes are allowed, must be connected along edges).

A000577

Number of triangular polyominoes (or triangular polyforms, or polyiamonds) with n cells (turning over is allowed, holes are allowed, must be connected along edges).

Terms

    a(0) =1a(1) =1a(2) =1a(3) =3a(4) =4a(5) =12a(6) =24a(7) =66a(8) =160a(9) =448a(10) =1186a(11) =3334a(12) =9235a(13) =26166a(14) =73983a(15) =211297a(16) =604107a(17) =1736328a(18) =5000593a(19) =14448984a(20) =41835738a(21) =121419260a(22) =353045291a(23) =1028452717a(24) =3000800627a(25) =8769216722a(26) =25661961898a(27) =75195166667a(28) =220605519559a(29) =647943626796

External references