Number of 2's in row n of A143589 (a Kolakoski fan).

Terms

a(0) =0a(1) =1a(2) =0a(3) =1a(4) =1a(5) =3a(6) =3a(7) =6a(8) =8a(9) =12a(10) =18a(11) =26a(12) =40a(13) =60a(14) =89a(15) =135a(16) =201a(17) =303a(18) =453a(19) =680a(20) =1022a(21) =1528a(22) =2299a(23) =3443a(24) =5176a(25) =7750a(26) =11642a(27) =17443a(28) =26172a(29) =39246