Number of poly-IH68-tiles (holes allowed) with n cells.

Terms

a(0) =1a(1) =1a(2) =4a(3) =10a(4) =34a(5) =110a(6) =388a(7) =1369a(8) =4982a(9) =18246a(10) =67727a(11) =253014a(12) =952275a(13) =3602743a(14) =13698525a(15) =52297602a(16) =200402285a(17) =770414503a(18) =2970385477a(19) =11482405741a(20) =44491816601a(21) =172766346508a(22) =672186393972