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 A050680 #21 Sep 04 2021 21:08:05 %S A050680 5,10,12,13,31,38,43,49,51,55,59,60,76,83,85,97,117,118 %N A050680 Positions of 3's in A048288. %H A050680 Patrick De Geest, <a href="http://www.worldofnumbers.com/revfact.htm">Reversed Smarandache Concatenated Numbers, Prime factors from n down to 1</a> %H A050680 M. Fleuren, <a href="http://www.gallup.unm.edu/~smarandache/michafleuren.htm">Factors and primes of Smarandache sequences</a>. %H A050680 M. Fleuren, <a href="http://www.gallup.unm.edu/~smarandache/micha.txt">Smarandache Factors and Reverse factors</a> %H A050680 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 A050680 Cf. A000422, A046462, A048288, A050679, A050681, A050682. %K A050680 nonn,base,hard,less,more %O A050680 1,1 %A A050680 _Patrick De Geest_, Aug 15 1999 %E A050680 a(13)-a(16) from _Sean A. Irvine_, Aug 17 2021 %E A050680 Offset changed to 1 by and a(17)-a(18) from _Jinyuan Wang_, Sep 04 2021