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 A278571 #9 Oct 19 2017 10:43:07 %S A278571 1,7,42,385,436,1530,3180,3625,8208,3767,10116,6699 %N A278571 Index of first occurrence of n in A278567. %Y A278571 Cf. A278567. %K A278571 nonn,more %O A278571 1,2 %A A278571 _N. J. A. Sloane_, Nov 27 2016 %E A278571 a(12) corrected by _Don Reble_, Nov 27 2016