To get a(n), replace 0's in the binary expansion of n with (-1) and interpret the result in base n.

Terms

a(0) =0a(1) =1a(2) =1a(3) =4a(4) =11a(5) =21a(6) =41a(7) =57a(8) =439a(9) =640a(10) =909a(11) =1222a(12) =1859a(13) =2354a(14) =2953a(15) =3616a(16) =61167a(17) =78303a(18) =98837a(19) =123121a(20) =152379a(21) =185641a(22) =224113a(23) =268227a(24) =344999a(25) =405601a(26) =473901a(27) =550423a(28) =637363a(29) =732483