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%I #12 Jan 27 2017 12:37:16
%S 1999291987030606810,2185352294922536801,3271704589845072613,
%T 6434410079699144336,12768830049399288682,41457129443403175403,
%U 71914259877895350817,143719619755790592734,581014717313707510075,1151030424627424920260,1771324671891665221771,3542550333873429453542,5996099577656760005995
%N Trajectory of 1999291987030606810 (the largest presently known "most delayed palindrome") under the "Reverse and Add!" operation.
%C 1999291987030606810 is the largest of the 126 presently known numbers that require exactly 261 steps to turn into a palindrome (see A281508). It is also the largest discovered "most delayed palindrome". The sequence reaches a 119-digit palindrome after 261 steps (see b-file). The number was obtained empirically using computer algorithms and was not reported before.
%D Popular Computing (Calabasas, CA), The 196 Problem, Vol. 3 (No. 30, Sep 1975).
%H Sergei D. Shchebetov, <a href="/A281509/b281509.txt">Table of n, a(n) for n = 0..261</a>
%H Jason Doucette, <a href="http://jasondoucette.com/worldrecords.html">World Records</a>
%H 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 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 C. W. Trigg, <a href="http://www.jstor.org/stable/2689178">Palindromes by Addition</a>, Mathematics Magazine, 40 (1967), 26-28.
%H 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 Wikipedia, <a href="https://en.wikipedia.org/wiki/Lychrel_number">Lychrel Number</a>
%H 196 and Other Lychrel Numbers, <a href="http://www.p196.org/">196 and Lychrel Number</a>
%H <a href="https://oeis.org/wiki/Index_to_OEIS:_Section_Res#RAA">Index entries for sequences related to Reverse and Add!</a>
%F a(n+1) = a(n) + rev(a(n)).
%F a(n) = A281507(n) for n>0. - _R. J. Mathar_, Jan 27 2017
%e a(1) = 1999291987030606810 + 186060307891929991 = 2185352294922536801.
%Y Cf. A023109, A033672, A065198, A065199, A065320, A065321, A065322, A065323, A065324, A065325, A065326, A065327, A070743, A072216, A072217, A072218, A281301, A281390, A281506, A281507, A281508.
%K nonn,base,less
%O 0,1
%A Andrey S. Shchebetov and _Sergei D. Shchebetov_, Jan 24 2017
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