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 A031958 #13 Aug 10 2021 14:27:10 %S A031958 38,39,40,41,48,51,52,53,54,56,58,59,60,62,63,65,66,68,69,70,73,75,76, %T A031958 77,78,81,82,83,90,91,94,95,96,97,99,101,102,103,105,106,109,110,112, %U A031958 113,114,116,118,119,120,121,124,125,132,133 %N A031958 Numbers with exactly three distinct base-6 digits. %Y A031958 CF. A007092. %K A031958 nonn,base %O A031958 1,1 %A A031958 _Clark Kimberling_