Number of Z-convex polyominoes with semiperimeter n.

Terms

a(0) =0a(1) =0a(2) =1a(3) =2a(4) =7a(5) =28a(6) =116a(7) =484a(8) =2022a(9) =8448a(10) =35290a(11) =147376a(12) =615228a(13) =2567060a(14) =10704976a(15) =44611804a(16) =185780308a(17) =773060804a(18) =3214225836a(19) =13352979316a(20) =55426067494a(21) =229870371888a(22) =952548347122