a(0) = 0; a(odd n) = 2n+1; a(even n) = a(n/2 - a(n-1)).

Terms

a(0) =0a(1) =3a(2) =-9a(3) =7a(4) =-9a(5) =11a(6) =27a(7) =15a(8) =-21a(9) =19a(10) =99a(11) =23a(12) =-33a(13) =27a(14) =63a(15) =31a(16) =-45a(17) =35a(18) =-117a(19) =39a(20) =-57a(21) =43a(22) =99a(23) =47a(24) =-69a(25) =51a(26) =-873a(27) =55a(28) =-81a(29) =59