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A281507
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Trajectory of 1186061987030929990 under the "Reverse and Add!" operation.
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8
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1186061987030929990, 2185352294922536801, 3271704589845072613, 6434410079699144336, 12768830049399288682, 41457129443403175403, 71914259877895350817, 143719619755790592734, 581014717313707510075, 1151030424627424920260, 1771324671891665221771
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OFFSET
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0,1
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COMMENTS
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1186061987030929990 is the largest of the first 126 numbers that require exactly 261 steps to turn into a palindrome (see A281506). 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.
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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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FORMULA
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a(n+1) = a(n) + rev(a(n)).
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EXAMPLE
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a(1) = 1186061987030929990 + 999290307891606811 = 2185352294922536801.
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MATHEMATICA
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NestList[#+IntegerReverse[#]&, 1186061987030929990, 20] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jan 17 2019 *)
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PROG
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(Magma) k:=1186061987030929990; [n eq 1 select k else Self(n-1) + Seqint(Reverse(Intseq(Self(n-1)))): n in [1..20]]; // Bruno Berselli, Jan 23 2017
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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.
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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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