Number of 1's when n is written in base -2.

Terms

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