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 A031088 #10 Apr 10 2020 21:42:19 %S A031088 0,9,27,45,63,81,99,117,135,153,154,157,160,163,166,169,172,175,178, %T A031088 180,207,234,261,288,315,342,369,396,397,400,403,406,409,412,415,418, %U A031088 421,423,450,477,504,531,558,585,612,639,640,643 %N A031088 Position of n-th 0 in A031087. %K A031088 nonn %O A031088 1,2 %A A031088 _Clark Kimberling_ %E A031088 Missing a(1)=0 inserted by _Sean A. Irvine_, Apr 10 2020