Number of polyiamonds with n cells, without holes.

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =4a(5) =12a(6) =24a(7) =66a(8) =159a(9) =444a(10) =1161a(11) =3226a(12) =8785a(13) =24453a(14) =67716a(15) =189309a(16) =528922a(17) =1484738a(18) =4172185a(19) =11756354a(20) =33174451a(21) =93795220a(22) =265565628a(23) =753060469a(24) =2138206966a(25) =6078931114a(26) =17302380313a(27) =49302121747a(28) =140627400927a(29) =401510058179