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 A043519 #14 Apr 24 2021 21:18:42 %S A043519 777,1777,2777,3777,4777,5777,6777,7077,7177,7277,7377,7477,7577,7677, %T A043519 7707,7717,7727,7737,7747,7757,7767,7770,7771,7772,7773,7774,7775, %U A043519 7776,7778,7779,7787,7797,7877,7977,8777,9777,10777 %N A043519 Numbers having three 7's in base 10. %H A043519 Daniel Starodubtsev, <a href="/A043519/b043519.txt">Table of n, a(n) for n = 1..10000</a> %t A043519 Select[Range[11000],DigitCount[#,10,7]==3&] (* _Harvey P. Dale_, Mar 25 2015 *) %Y A043519 Subsequence of A011537. %K A043519 nonn,base %O A043519 1,1 %A A043519 _Clark Kimberling_