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 A043501 #17 Apr 24 2021 21:09:52 %S A043501 3,13,23,30,31,32,34,35,36,37,38,39,43,53,63,73,83,93,103,113,123,130, %T A043501 131,132,134,135,136,137,138,139,143,153,163,173,183,193,203,213,223, %U A043501 230,231,232,234,235,236,237,238,239,243,253 %N A043501 Numbers having one 3 in base 10. %H A043501 Enrique Pérez Herrero, <a href="/A043501/b043501.txt">Table of n, a(n) for n = 1..2000</a> %H A043501 <a href="/index/Ar#10-automatic">Index entries for 10-automatic sequences</a>. %t A043501 Select[Range[9000],DigitCount[#,10,3]==1&] (* _Enrique Pérez Herrero_, Nov 29 2013 *) %Y A043501 Cf. A043489, A043493, A043497, A043505, A043509, A043513, A043517, A043521, A043525, A011533. %K A043501 nonn,base,easy %O A043501 1,1 %A A043501 _Clark Kimberling_