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 A050681 #19 Sep 04 2021 21:08:11 %S A050681 8,14,16,19,21,23,37,57,67,70,79,88,106 %N A050681 Positions of 4's in A048288. %H A050681 Patrick De Geest, <a href="http://www.worldofnumbers.com/revfact.htm">Reversed Smarandache Concatenated Numbers, Prime factors from n down to 1</a> %H A050681 M. Fleuren, <a href="http://www.gallup.unm.edu/~smarandache/michafleuren.htm">Factors and primes of Smarandache sequences</a>. %H A050681 M. Fleuren, <a href="http://www.gallup.unm.edu/~smarandache/micha.txt">Smarandache Factors and Reverse factors</a> %H A050681 Carlos Rivera, <a href="http://www.primepuzzles.net/puzzles/puzz_008.htm">Puzzle 8. Primes by Listing</a>, The Prime Puzzles and Problems Connection. %Y A050681 Cf. A000422, A046463, A048288, A050679, A050680, A050682. %K A050681 nonn,base,hard,less,more %O A050681 1,1 %A A050681 _Patrick De Geest_, Aug 15 1999 %E A050681 a(9)-a(13) from _Sean A. Irvine_, Aug 17 2021 %E A050681 Offset changed to 1 by _Jinyuan Wang_, Sep 04 2021