a(2*n) = n+1, a(2*n-1) = 2*n-1.

Terms

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