Number of pseudo-square convex polyominoes with semiperimeter n.

Terms

a(0) =1a(1) =12a(2) =44a(3) =142a(4) =399a(5) =1044a(6) =2571a(7) =6168a(8) =14357a(9) =32786a(10) =73746a(11) =163872a(12) =360462a(13) =786468a(14) =1703949a(15) =3670040a(16) =7864353a(17) =16777260a(18) =35651579a(19) =75497508a(20) =159383591a(21) =335544350a(22) =704643087a(23) =1476395064a(24) =3087007733a(25) =6442451004a(26) =13421772816a(27) =27917287460a(28) =57982058547a(29) =120259084318