Successive left concatenation of floor(k/2) beginning with n until we reach 1.

Terms

a(0) =1a(1) =21a(2) =31a(3) =421a(4) =521a(5) =631a(6) =731a(7) =8421a(8) =9421a(9) =10521a(10) =11521a(11) =12631a(12) =13631a(13) =14731a(14) =15731a(15) =168421a(16) =178421a(17) =189421a(18) =199421a(19) =2010521a(20) =2110521a(21) =2211521a(22) =2311521a(23) =2412631a(24) =2512631a(25) =2613631a(26) =2713631a(27) =2814731a(28) =2914731a(29) =3015731