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 A083835 #8 Aug 23 2014 13:39:07 %S A083835 1,9,99,121,131,999,9999,12021,12121,13031,13131,99999,999999,1202021, %T A083835 1203021,1212121,1213121,1302031,1303031,1312131,1313131,9999999, %U A083835 99999999,120202021,120212021,120303021,120313021,121202121,121212121 %N A083835 Palindromes n such that 6n + 1 is also a palindrome. %Y A083835 Cf. A083829, A083830, A083832, A083834, A083836. %K A083835 base,nonn %O A083835 1,2 %A A083835 _Amarnath Murthy_ and Meenakshi Srikanth (menakan_s(AT)yahoo.com), May 09 2003 %E A083835 Corrected and extended by _Ray Chandler_, May 21 2003