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 A051806 #8 Jul 02 2021 11:44:01 %S A051806 4,14,22,27,39,40,41,58,72,85,89,93,98,104,114,122,127,139,140,141, %T A051806 158,172,185,189,193,198,202,207,212,217,220,221,245,249,254,266,270, %U A051806 271,277,294,309,319,333,338,346,364,379,383 %N A051806 Numbers with nonzero multiplicative digital root 4. %H A051806 <a href="/index/Ar#10-automatic">Index entries for 10-automatic sequences</a>. %F A051806 A051802^-1(4) %t A051806 mdr4Q[n_]:=NestWhile[Times@@(IntegerDigits[#]/.(0->1))&,n,#>9&]==4; Select[ Range[ 400],mdr4Q] (* _Harvey P. Dale_, Jul 02 2021 *) %Y A051806 Part of histogram of A051802. %K A051806 nonn,easy,base %O A051806 1,1 %A A051806 _Dan Hoey_, Dec 09 1999