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 A020953 #6 May 05 2019 21:50:54 %S A020953 0,10,20,40,42,160,82,84,162,166,164,172,170,324,328,348,332,330,338, %T A020953 700,340,652,650,664,662,658,666,1290,660,676,684,1302,1298,682,1306, %U A020953 1338,1300,2584,1348,1320,1316,2626,1324,1332 %N A020953 Least k such that A020951(k) = n. %K A020953 nonn %O A020953 1,2 %A A020953 _Clark Kimberling_ %E A020953 Title simplified, missing a(21), a(38), a(42) inserted by _Sean A. Irvine_, May 05 2019