a(n) is the number of odd polyominoes with n cells.

Terms

a(0) =0a(1) =1a(2) =3a(3) =11a(4) =35a(5) =108a(6) =380a(7) =1348a(8) =5014a(9) =18223a(10) =67634a(11) =252849a(12) =950346a(13) =3602437a(14) =13697333a(15) =52293534a(16) =200399576a(17) =770410271a(18) =2970369338a(19) =11482572252a(20) =44492417777a(21) =172766286339a(22) =672186167762