a(0) = 0, a(n) = a(n-1) XOR -n.

Terms

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