Hofstadter G-sequence: a(0) = 0; a(n) = n - a(a(n-1)) for n > 0.

Terms

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