Number of poly-IH64-tiles (holes allowed) with n cells.

Terms

a(0) =1a(1) =2a(2) =4a(3) =12a(4) =35a(5) =116a(6) =392a(7) =1390a(8) =4998a(9) =18321a(10) =67791a(11) =253288a(12) =952527a(13) =3603761a(14) =13699516a(15) =52301427a(16) =200406183a(17) =770429000a(18) =2970400815a(19) =11482461055a(20) =44491876993a(21) =172766558719a(22) =672186631950