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 A043502 #24 Apr 24 2021 21:10:02 %S A043502 33,133,233,303,313,323,330,331,332,334,335,336,337,338,339,343,353, %T A043502 363,373,383,393,433,533,633,733,833,933,1033,1133,1233,1303,1313, %U A043502 1323,1330,1331,1332,1334,1335,1336,1337,1338,1339,1343 %N A043502 Numbers having two 3's in base 10. %H A043502 Daniel Starodubtsev, <a href="/A043502/b043502.txt">Table of n, a(n) for n = 1..10000</a> %t A043502 Select[Range[5000], DigitCount[#, 10, 3]==2&] (* _Vincenzo Librandi_, Jul 01 2015 *) %Y A043502 Subsequence of A011533. %K A043502 nonn,base %O A043502 1,1 %A A043502 _Clark Kimberling_