Number of n X 3 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 1 0 and 1 1 1 vertically.

Terms

a(0) =6a(1) =36a(2) =60a(3) =126a(4) =234a(5) =456a(6) =896a(7) =1722a(8) =3360a(9) =6512a(10) =12642a(11) =24570a(12) =47644a(13) =92568a(14) =179690a(15) =348800a(16) =677340a(17) =1314846a(18) =2552850a(19) =4956336a(20) =9622272a(21) =18681842a(22) =36269696a(23) =70416640a(24) =136712226a(25) =265421170a(26) =515308500a(27) =1000454184a(28) =1942349698a(29) =3771013664