Number of column-convex polyominoes with perimeter 2n+2.

Terms

a(0) =1a(1) =2a(2) =7a(3) =28a(4) =122a(5) =558a(6) =2641a(7) =12822a(8) =63501a(9) =319554a(10) =1629321a(11) =8399092a(12) =43701735a(13) =229211236a(14) =1210561517a(15) =6432491192a(16) =34364148528a(17) =184463064936a(18) =994430028087