Number of one-sided polyominoes with n cells.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =7a(5) =18a(6) =60a(7) =196a(8) =704a(9) =2500a(10) =9189a(11) =33896a(12) =126759a(13) =476270a(14) =1802312a(15) =6849777a(16) =26152418a(17) =100203194a(18) =385221143a(19) =1485200848a(20) =5741256764a(21) =22245940545a(22) =86383382827a(23) =336093325058