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 A062221 #17 Oct 31 2019 01:23:15 %S A062221 3,5,9,17,71,99,243,7595,9273,53847 %N A062221 Numbers k such that the smoothly undulating palindromic number (72*10^k - 27)/99 is a prime. %C A062221 Prime versus probable prime status and proofs are given in the author's table. %C A062221 No further terms < 100000. - _Ray Chandler_, Aug 17 2011 %H A062221 Patrick De Geest, <a href="http://www.worldofnumbers.com/undulat.htm#supp727">SUPP Reference Table - 727</a> %H A062221 <a href="/index/Pri#pri_supp">Index entries for sequences related to smoothly undulating palindromic primes</a> %e A062221 k=17 -> (72*10^17 - 27)/99 = 72727272727272727. %Y A062221 Cf. A062209-A062232, A059758, A032758. %K A062221 nonn,base,more %O A062221 1,1 %A A062221 _Patrick De Geest_ and Hans Rosenthal (Hans.Rosenthal(AT)t-online.de), Jun 15 2001 %E A062221 a(10)=53847 from _Patrick De Geest_, Aug 06 2004 %E A062221 Edited by _Ray Chandler_, Aug 17 2011