a(0) = a(1) = 1; thereafter a(2*n+1) = 2*a(2*n) - a(2*n-1), a(2*n) = 4*a(2*n-1) - a(2*n-2).

Terms

a(0) =1a(1) =1a(2) =3a(3) =5a(4) =17a(5) =29a(6) =99a(7) =169a(8) =577a(9) =985a(10) =3363a(11) =5741a(12) =19601a(13) =33461a(14) =114243a(15) =195025a(16) =665857a(17) =1136689a(18) =3880899a(19) =6625109a(20) =22619537a(21) =38613965a(22) =131836323a(23) =225058681a(24) =768398401a(25) =1311738121a(26) =4478554083a(27) =7645370045a(28) =26102926097a(29) =44560482149