a(n) is the number of polyominoes with n edges, including inner edges.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =0a(5) =0a(6) =1a(7) =0a(8) =0a(9) =2a(10) =0a(11) =1a(12) =4a(13) =0a(14) =1a(15) =11a(16) =1a(17) =7a(18) =27a(19) =4a(20) =21a(21) =85a(22) =21a(23) =92a(24) =264a(25) =89a(26) =345a(27) =914a(28) =394a(29) =1405