This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A009470 #18 Sep 08 2022 08:44:37
%S A009470 18,216,324,432,540,648,756,864,972,1080,1188,1296,13104,14112,15120,
%T A009470 16128,17136,18144,19152,20160,21168,22176,23184,24192,25200,26208,
%U A009470 27216,28224,29232,30240,31248,32256,33264,34272,35280,36288,37296,38304,39312
%N A009470 a(n) is the concatenation of n and 8n.
%C A009470 All terms are divisible by 9. - _Michel Marcus_, Sep 21 2015
%H A009470 Vincenzo Librandi, <a href="/A009470/b009470.txt">Table of n, a(n) for n = 1..1000</a>
%t A009470 nxt[n_]:=Module[{idn=IntegerDigits[n], idn8=IntegerDigits[8n]}, FromDigits[Join[idn,idn8]]]; Array[nxt, 100] (* _Vincenzo Librandi_, Feb 04 2014 *)
%o A009470 (Magma) [Seqint(Intseq(8*n) cat Intseq(n)): n in [1..50]]; // _Vincenzo Librandi_, Feb 04 2014
%o A009470 (PARI) a(n) = eval(Str(n, 8*n)); \\ _Michel Marcus_, Sep 21 2015
%Y A009470 Cf. concatenation of n and k*n: A020338 (k=1), A019550 (k=2), A019551 (k=3), A019552 (k=4), A019553 (k=5), A009440 (k=6), A009441 (k=7), this sequence (k=8), A009474 (k=9).
%K A009470 nonn,base,less,easy
%O A009470 1,1
%A A009470 _David W. Wilson_