There are a(n) 2's between successive 1's.

Terms

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