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 A281508 #7 Jan 24 2017 20:52:52 %S A281508 1999290307891606810,1999290317791606810,1999290327691606810, %T A281508 1999290337591606810,1999290347491606810,1999290357391606810, %U A281508 1999290367291606810,1999290377191606810,1999290387091606810,1999290407881606810,1999290417781606810,1999290427681606810,1999290437581606810 %N A281508 Numbers requiring exactly 261 'Reverse and Add' steps to reach a palindrome. %C A281508 The sequence starts with 1999290307891606810 and continues for another 125 terms (none previously reported, including the first term) each turning into a 119-digit palindrome after 261 steps until the sequence ends with 1999291987030606810. The distance between successive terms in the reported sequence has 9000000 as the greatest common divisor. No further numbers beyond 1999291987030606810 belonging to the same sequence are known, discovered or reported. Moreover, 1999291987030606810 is currently the largest discovered "most delayed palindrome". The sequence was found empirically using computer modeling algorithms. %C A281508 It is only a conjecture that there are no further terms. - _N. J. A. Sloane_, Jan 24 2017 %D A281508 Popular Computing (Calabasas, CA), The 196 Problem, Vol. 3 (No. 30, Sep 1975). %H A281508 Sergei D. Shchebetov, <a href="/A281508/b281508.txt">Table of n, a(n) for n = 1..126</a> %H A281508 Jason Doucette, <a href="http://jasondoucette.com/worldrecords.html">World Records</a> %H A281508 Yutaka Nishiyama, <a href="http://www.ijpam.eu/contents/2012-80-3/9/index.html">Numerical Palindromes and the 196 Problem</a>, International Journal of Pure and Applied Mathematics, Volume 80 No. 3 2012, 375-384. %H A281508 R. Styer, <a href="http://www41.homepage.villanova.edu/robert.styer/PalindromePaper1986.pdf">The Palindromic Conjecture and the Fibonacci Sequence</a>, Villanova University, 1986, 1-11. %H A281508 C. W. Trigg, <a href="http://www.jstor.org/stable/2689178">Palindromes by Addition</a>, Mathematics Magazine, 40 (1967), 26-28. %H A281508 C. W. Trigg, <a href="http://www.jstor.org/stable/2688651">More on Palindromes by Reversal-Addition</a>, Mathematics Magazine, 45 (1972), 184-186. %H A281508 Wikipedia, <a href="https://en.wikipedia.org/wiki/Lychrel_number">Lychrel Number</a> %H A281508 196 and Other Lychrel Numbers, <a href="http://www.p196.org/">196 and Lychrel Number</a> %H A281508 <a href="https://oeis.org/wiki/Index_to_OEIS:_Section_Res#RAA">Index entries for sequences related to Reverse and Add!</a> %e A281508 Each term requires exactly 261 steps to turn into a 119-digit palindrome, the last term of A281509, and is separated by some multiples of 9000000 from the adjacent sequence terms. %Y A281508 Cf. A023109, A033672, A065198, A065199, A065320, A065321, A065322, A065323, A065324, A065325, A065326, A065327, A070743, A072216, A072217, A072218, A281301, A281390, A281506, A281507. %K A281508 nonn,base %O A281508 1,1 %A A281508 Andrey S. Shchebetov and _Sergei D. Shchebetov_, Jan 24 2017