Triangular polyominoes (n-iamonds) without bilateral symmetry (holes are allowed).

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =2a(5) =7a(6) =19a(7) =54a(8) =147a(9) =418a(10) =1150a(11) =3254a(12) =9138a(13) =25953a(14) =73717a(15) =210719a(16) =603370a(17) =1734739a(18) =4998542a(19) =14444576a(20) =41829991a(21) =121406927a(22) =353029078a(23) =1028417980a(24) =3000754648a(25) =8769118355a(26) =25661830891a(27) =75194886765a(28) =220605144778a(29) =647942827064