Number of board-pair-pile polyominoes with n cells.

Terms

a(0) =1a(1) =2a(2) =6a(3) =19a(4) =63a(5) =216a(6) =760a(7) =2723a(8) =9880a(9) =36168a(10) =133237a(11) =492993a(12) =1829670a(13) =6804267a(14) =25336611a(15) =94416842a(16) =351989967a(17) =1312471879a(18) =4894023222a(19) =18248301701a(20) =68036380665a(21) =253638655582a(22) =945464013411