Generalized nim sum n + n in base 4.

Terms

a(0) =0a(1) =2a(2) =0a(3) =2a(4) =8a(5) =10a(6) =8a(7) =10a(8) =0a(9) =2a(10) =0a(11) =2a(12) =8a(13) =10a(14) =8a(15) =10a(16) =32a(17) =34a(18) =32a(19) =34a(20) =40a(21) =42a(22) =40a(23) =42a(24) =32a(25) =34a(26) =32a(27) =34a(28) =40a(29) =42