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 A031987 #10 Aug 10 2021 21:16:04 %S A031987 10234,10235,10236,10237,10238,10239,10243,10245,10246,10247,10248, %T A031987 10249,10253,10254,10256,10257,10258,10259,10263,10264,10265,10267, %U A031987 10268,10269,10273,10274,10275,10276,10278,10279 %N A031987 Numbers with exactly five distinct base-10 digits. %K A031987 nonn,base %O A031987 1,1 %A A031987 _Clark Kimberling_