a(n) = if n=0 then 0 else a(floor(n/2))+n*(-1)^(n mod 2).

Terms

a(0) =0a(1) =-1a(2) =1a(3) =-4a(4) =5a(5) =-4a(6) =2a(7) =-11a(8) =13a(9) =-4a(10) =6a(11) =-15a(12) =14a(13) =-11a(14) =3a(15) =-26a(16) =29a(17) =-4a(18) =14a(19) =-23a(20) =26a(21) =-15a(22) =7a(23) =-38a(24) =38a(25) =-11a(26) =15a(27) =-38a(28) =31a(29) =-26