Number of d+/d- diagonally convex polyominoes with n cells.

Terms

a(0) =1a(1) =2a(2) =6a(3) =19a(4) =61a(5) =196a(6) =630a(7) =2024a(8) =6499a(9) =20860a(10) =66941a(11) =214797a(12) =689201a(13) =2211347a(14) =7095226a(15) =22765414a(16) =73044113a(17) =234366327a(18) =751978494a(19) =2412768983a(20) =7741517800a(21) =24839137696a(22) =79697907919a(23) =255715662623