Kolakoski sequence: a(n) is length of n-th run; a(1) = 1; sequence consists just of 1's and 2's.

Terms

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