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 A050688 #31 Sep 04 2021 10:09:10 %S A050688 8,9,15,17,18,26,27,35,36,44,45,53,54,56,62,63,71,72,80,81,89,90,98, %T A050688 99,107,108,109 %N A050688 Numbers k such that A000422(k) is nonsquarefree. %H A050688 Patrick De Geest, <a href="http://www.worldofnumbers.com/revfact.htm">Reversed Smarandache Concatenated Numbers, Prime factors from n down to 1</a> %H A050688 M. Fleuren, <a href="http://www.gallup.unm.edu/~smarandache/michafleuren.htm">Factors and primes of Smarandache sequences</a>. %H A050688 M. Fleuren, <a href="http://www.gallup.unm.edu/~smarandache/micha.txt">Smarandache Factors and Reverse factors</a> %H A050688 Carlos Rivera, <a href="http://www.primepuzzles.net/puzzles/puzz_008.htm">Puzzle 8. Primes by Listing</a>, The Prime Puzzles & Problems Connection. %e A050688 a(2)=9 because 987654321 = 3^2 * 17^2 * 379721. %Y A050688 Cf. A013929, A000422, A048288, A048342, A050687, A050675. %K A050688 nonn,base,hard %O A050688 1,1 %A A050688 _Patrick De Geest_, Aug 15 1999 %E A050688 Definition corrected by _Charles R Greathouse IV_, Sep 20 2012 %E A050688 a(17)-a(24) and name corrected by _Sean A. Irvine_, Aug 17 2021 %E A050688 a(25)-a(27) from _Daniel Suteu_, Aug 18 2021