Number of achiral triangular n-ominoes (n-iamonds) (holes are allowed).

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =2a(5) =5a(6) =5a(7) =12a(8) =13a(9) =30a(10) =36a(11) =80a(12) =97a(13) =213a(14) =266a(15) =578a(16) =737a(17) =1589a(18) =2051a(19) =4408a(20) =5747a(21) =12333a(22) =16213a(23) =34737a(24) =45979a(25) =98367a(26) =131007a(27) =279902a(28) =374781a(29) =799732