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%I #12 Sep 17 2018 13:29:34
%S 29,112,233,556,1112,2233,5555,1111,2222,4444,8888,16777,34589,112333,
%T 444455,889999,1788899,1177777,4558889,13444447,77888888,156667777,
%U 233444489,1112278888,11999,11119,1223,4444,8888,16777,34589,112333,444455,889999,1788899
%N RATS: Reverse Add Then Sort the digits applied to previous term, starting with 29.
%C A114616(1) = 29 is the smallest starting number for a RATS trajectory leading to a cycle of length 18: A114611(29) = 18;
%C a(n + 18) = a(n) for n > 9.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/RATSSequence.html">RATS Sequence</a>
%H <a href="/index/Rec#order_18">Index entries for linear recurrences with constant coefficients</a>, signature (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1).
%F a(n + 1) = A036839(a(n)).
%t NestList[FromDigits[Sort[IntegerDigits[#+IntegerReverse[#]]]]&,29,40] (* or *) PadRight[{29,112,233,556,1112,2233,5555,1111,2222},50,{4558889,13444447,77888888,156667777,233444489,1112278888,11999,11119,1223,4444,8888,16777,34589,112333,444455,889999,1788899,1177777}] (* _Harvey P. Dale_, Sep 17 2018 *)
%o (Haskell)
%o a209880 n = a209880_list !! (n-1)
%o a209880_list = iterate a036839 29
%Y Cf. A004000, A066710, A209878, A066711, A209879.
%K nonn,base
%O 1,1
%A _Reinhard Zumkeller_, Mar 14 2012
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