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 A045921 #10 Mar 27 2021 22:38:23 %S A045921 13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,131, %T A045921 151,191,313,353,373,757,797,919,35353,95959,919191919,979797979, %U A045921 91919191919,151515151515151,737373737373737,75757575757575757,91919191919191919 %N A045921 Erroneous version of A032758. %K A045921 dead %O A045921 1,1