a(1)=0, a(2n) = a(n)+1, a(2n+1) = 10*a(n+1).

Terms

a(0) =0a(1) =1a(2) =10a(3) =2a(4) =100a(5) =11a(6) =20a(7) =3a(8) =1000a(9) =101a(10) =110a(11) =12a(12) =200a(13) =21a(14) =30a(15) =4a(16) =10000a(17) =1001a(18) =1010a(19) =102a(20) =1100a(21) =111a(22) =120a(23) =13a(24) =2000a(25) =201a(26) =210a(27) =22a(28) =300a(29) =31