a(n) is the reverse concatenation of divisors of n.

Terms

a(0) =1a(1) =21a(2) =31a(3) =421a(4) =51a(5) =6321a(6) =71a(7) =8421a(8) =931a(9) =10521a(10) =111a(11) =1264321a(12) =131a(13) =14721a(14) =15531a(15) =168421a(16) =171a(17) =1896321a(18) =191a(19) =20105421a(20) =21731a(21) =221121a(22) =231a(23) =2412864321a(24) =2551a(25) =261321a(26) =27931a(27) =28147421a(28) =291a(29) =30151065321