Hofstadter-Conway $10000 sequence: a(n) = a(a(n-1)) + a(n-a(n-1)) with a(1) = a(2) = 1.

Terms

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