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A281508
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Numbers requiring exactly 261 'Reverse and Add' steps to reach a palindrome.
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4
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1999290307891606810, 1999290317791606810, 1999290327691606810, 1999290337591606810, 1999290347491606810, 1999290357391606810, 1999290367291606810, 1999290377191606810, 1999290387091606810, 1999290407881606810, 1999290417781606810, 1999290427681606810, 1999290437581606810
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OFFSET
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1,1
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COMMENTS
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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.
It is only a conjecture that there are no further terms. - N. J. A. Sloane, Jan 24 2017
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REFERENCES
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Popular Computing (Calabasas, CA), The 196 Problem, Vol. 3 (No. 30, Sep 1975).
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LINKS
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EXAMPLE
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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.
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CROSSREFS
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Cf. A023109, A033672, A065198, A065199, A065320, A065321, A065322, A065323, A065324, A065325, A065326, A065327, A070743, A072216, A072217, A072218, A281301, A281390, A281506, A281507.
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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