Generalized nim sum n + n in base 9.

Terms

a(0) =0a(1) =2a(2) =4a(3) =6a(4) =8a(5) =1a(6) =3a(7) =5a(8) =7a(9) =18a(10) =20a(11) =22a(12) =24a(13) =26a(14) =19a(15) =21a(16) =23a(17) =25a(18) =36a(19) =38a(20) =40a(21) =42a(22) =44a(23) =37a(24) =39a(25) =41a(26) =43a(27) =54a(28) =56a(29) =58