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 A031257 #6 Jul 07 2024 23:05:41 %S A031257 2,12,13,15,17,22,37,48,51,52,67,82,84,87,90,97,98,101,104,107,110, %T A031257 112,113,116,119,122,123,125,126,127,128,131,134,142,157,159,162,165, %U A031257 172,192,207,211,212,232,252,255,259,263,272,292 %N A031257 Position of n-th 3 in A031253. %Y A031257 Cf. A031253. %K A031257 nonn %O A031257 1,1 %A A031257 _Clark Kimberling_