a(n) = 6*a(n-2) - a(n-4) for n > 4, with a(1)=1, a(2)=0, a(3)=3, a(4)=2.

Terms

a(0) =1a(1) =0a(2) =3a(3) =2a(4) =17a(5) =12a(6) =99a(7) =70a(8) =577a(9) =408a(10) =3363a(11) =2378a(12) =19601a(13) =13860a(14) =114243a(15) =80782a(16) =665857a(17) =470832a(18) =3880899a(19) =2744210a(20) =22619537a(21) =15994428a(22) =131836323a(23) =93222358a(24) =768398401a(25) =543339720a(26) =4478554083a(27) =3166815962a(28) =26102926097a(29) =18457556052