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 A031998 #15 May 05 2020 10:29:13 %S A031998 1,2,3,4,6,7,8,9,12,13,18,21,22,24,25,26,27,36,39,40,54,63,66,67,72, %T A031998 75,76,78,79,80,81,108,117,120,121,162,189,198,201,202,216,225,228, %U A031998 229,234,237,238,240,241,242,243,324,351,360,363 %N A031998 Duplicate of A023759. %Y A031998 Cf. A023759. %K A031998 dead %O A031998 1,2