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 A034056 #30 May 19 2025 08:16:46
%S A034056 9,19,33,91,119,133,191,313,331,911,1119,1133,1191,1313,1331,1911,
%T A034056 3113,3131,3311,9111,11119,11133,11191,11313,11331,11911,13113,13131,
%U A034056 13311,19111,31113,31131,31311,33111,91111,111119,111133,111191,111313,111331
%N A034056 Numbers with multiplicative digital root value 9.
%C A034056 Numbers with one 9 or two 3s, and zero or more 1s. - _Daniel Forgues_, Oct 09 2011
%H A034056 Harvey P. Dale, <a href="/A034056/b034056.txt">Table of n, a(n) for n = 1..1000</a>
%H A034056 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/MultiplicativeDigitalRoot.html">Multiplicative Digital Root</a>
%H A034056 <a href="/index/Ar#10-automatic">Index entries for 10-automatic sequences</a>.
%F A034056 There are n(n+1)(n+2)/6 elements up to 10^n, so a(n) is about 10^sqrt(6n).
%t A034056 Module[{nn=6,ne,te},ne=Union[FromDigits/@Flatten[Permutations/@Table[PadRight[{9},n,1],{n,nn}],1]];te=Rest[Union[FromDigits/@ Flatten[ Permutations/@Table[PadRight[{3,3},n,1],{n,nn}],1]]];Join[ne,te]]//Sort (* _Harvey P. Dale_, Apr 14 2025 *)
%Y A034056 Cf. A031347.
%Y A034056 Cf. A034048, A002275, A034049, A034050, A034051, A034052, A034053, A034054, A034055, A034056 (numbers having multiplicative digital roots 0-9).
%K A034056 nonn,base,easy
%O A034056 1,1
%A A034056 _Patrick De Geest_, Sep 15 1998