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 A031240 #6 Mar 01 2023 15:31:13 %S A031240 4,13,23,33,36,38,40,42,43,44,57,72,87,102,106,109,112,115,117,118, %T A031240 132,147,162,177,181,184,187,190,192,193,207,222,237,252,256,259,262, %U A031240 265,267,268,272,275,278,281,282,284,287,290,293 %N A031240 Position of n-th 4 in A031235. %Y A031240 Cf. A031235. %K A031240 nonn %O A031240 1,1 %A A031240 _Clark Kimberling_