The regular paper-folding (or dragon curve) sequence. Alphabet {2,1}.

Terms

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