a(n) is the total sum of area over all (>=,>=)-polyominoes of length n.

Terms

a(0) =0a(1) =1a(2) =5a(3) =19a(4) =66a(5) =218a(6) =701a(7) =2215a(8) =6919a(9) =21438a(10) =66034a(11) =202502a(12) =618892a(13) =1886433a(14) =5737755a(15) =17421735a(16) =52823013a(17) =159970938a(18) =483979572a(19) =1463006976a(20) =4419285573a(21) =13340964849a(22) =40252007970a(23) =121389925346a(24) =365929470596