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 A286481 #32 Jul 23 2025 15:41:55 %S A286481 1003062289999939142,1003062299899939142,1003062389989939142, %T A286481 1003062399889939142,1003062489979939142,1003062499879939142, %U A286481 1003062589969939142,1003062599869939142,1003062689959939142,1003062699859939142,1003062789949939142,1003062799849939142,1003062889939939142,1003062899839939142,1003062989929939142,1003062999829939142 %N A286481 Numbers which require exactly 260 'Reverse and Add' steps to reach a palindrome. %C A286481 The sequence starts with 1003062289999939142 (the 19-digit number discovered by Vaughn Suite on Mar 19 2006) and continues for another 430079 terms (none previously reported) each turning into a 119-digit palindrome after 260 steps until the sequence ends with 3419399999822603000 (see a-file). No further numbers beyond 3419399999822603000 belonging to the same sequence exist. The sequence was predicted theoretically and found empirically using computer modeling algorithms. For the first 100 terms of the sequence see b-file. %D A286481 Popular Computing (Calabasas, CA), The 196 Problem, Vol. 3 (No. 30, Sep 1975). %H A286481 Sergei D. Shchebetov, <a href="/A286481/b286481.txt">Table of n, a(n) for n = 1..99</a> %H A286481 Jason Doucette, <a href="http://jasondoucette.com/worldrecords.html">World Records</a> %H A286481 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 A286481 Sergei D. Shchebetov, <a href="/A286481/a286481-430080.zip">430080 terms (zipped file)</a> %H A286481 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 A286481 C. W. Trigg, <a href="http://www.jstor.org/stable/2689178">Palindromes by Addition</a>, Mathematics Magazine, 40 (1967), 26-28. %H A286481 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 A286481 Wikipedia, <a href="https://en.wikipedia.org/wiki/Lychrel_number">Lychrel Number</a> %H A286481 196 and Other Lychrel Numbers, <a href="http://www.p196.org/">196 and Lychrel Number</a> %H A286481 <a href="https://oeis.org/wiki/Index_to_OEIS:_Section_Res#RAA">Index entries for sequences related to Reverse and Add!</a> %F A286481 a(n+1) = a(n) + rev(a(n)). %e A286481 a(1) = 1003062289999939142 + 2419399999822603001 = 3422462289822542143 %Y A286481 Cf. A023109, A033672, A065198, A065199, A065320, A065321, A065322, A065323, A065324, A065325, A065326, A065327, A070743, A072216, A072217, A072218, A281301, A281390, A281506, A281507, A281508, A281509. %K A286481 nonn,base %O A286481 1,1 %A A286481 Andrey S. Shchebetov and _Sergei D. Shchebetov_, May 12 2017