Number of fixed polypons with n cells (division into triangles is significant).

Terms

a(0) =6a(1) =9a(2) =14a(3) =24a(4) =42a(5) =77a(6) =144a(7) =276a(8) =538a(9) =1065a(10) =2136a(11) =4321a(12) =8790a(13) =17967a(14) =36890a(15) =76050a(16) =157380a(17) =326824a(18) =680880a(19) =1422570a(20) =2979572a(21) =6254175a(22) =13153242a(23) =27712901a(24) =58487796a(25) =123632910a(26) =261722022a(27) =554800719a(28) =1177553610a(29) =2502256578