Axially symmetric n-celled polyominoes with 1 hole.

Terms

a(0) =1a(1) =3a(2) =8a(3) =25a(4) =45a(5) =137a(6) =221a(7) =650a(8) =1006a(9) =2857a(10) =4370a(11) =12050a(12) =18417a(13) =49516a(14) =76037a(15) =200184a(16) =309411a(17) =800440a(18) =1245934a(19) =3176482