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

Terms

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