a(n) is the number of fixed polyominoes with sprawl n.

Terms

a(0) =1a(1) =0a(2) =0a(3) =0a(4) =0a(5) =1a(6) =0a(7) =0a(8) =2a(9) =0a(10) =4a(11) =2a(12) =9a(13) =9a(14) =22a(15) =32a(16) =66a(17) =104a(18) =200a(19) =348a(20) =646a(21) =1172a(22) =2144a(23) =3964a(24) =7285a(25) =13581a(26) =25136a(27) =47070a(28) =87700a(29) =164764