(Even numbers in Hofstadter Q-sequence)/2.

Terms

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