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 A043512 #12 Apr 24 2021 21:15:39 %S A043512 5555,15555,25555,35555,45555,50555,51555,52555,53555,54555,55055, %T A043512 55155,55255,55355,55455,55505,55515,55525,55535,55545,55550,55551, %U A043512 55552,55553,55554,55556,55557,55558,55559,55565,55575 %N A043512 Numbers having four 5's in base 10. %H A043512 Daniel Starodubtsev, <a href="/A043512/b043512.txt">Table of n, a(n) for n = 1..10000</a> %Y A043512 Subsequence of A011535. %K A043512 nonn,base %O A043512 1,1 %A A043512 _Clark Kimberling_