Number of polyiamonds with n cells, with holes.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =0a(8) =1a(9) =4a(10) =25a(11) =108a(12) =450a(13) =1713a(14) =6267a(15) =21988a(16) =75185a(17) =251590a(18) =828408a(19) =2692630a(20) =8661287a(21) =27624040a(22) =87479663a(23) =275392248a(24) =862593661a(25) =2690285608a(26) =8359581585a(27) =25893044920a(28) =79978118632a(29) =246433568617