A209879 - OEIS

%I #15 Aug 25 2015 14:57:14

%S 6999,15699,11355,66666,123333,445566,111111,222222,444444,888888,

%T 1677777,3455589,11112333,33444444,77778888,156666666,123333378,

%U 666669999,1356666666,123333789,11111667,22777788,11115555,66666666,123333333,445566666,111122223

%N RATS: Reverse Add Then Sort the digits applied to previous term, starting with 6999.

%C A114615(1) = 6999 is the smallest starting number for a RATS trajectory leading to a cycle of length 14: A114611(6999) = 14;

%C a(n + 14) = a(n) for n > 25.

%H Reinhard Zumkeller, <a href="/A209879/b209879.txt">Table of n, a(n) for n = 1..100</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/RATSSequence.html">RATS Sequence</a>

%H <a href="/index/Rec#order_14">Index entries for linear recurrences with constant coefficients</a>, signature (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1).

%F a(n + 1) = A036839(a(n)).

%t rats[n_]:=Module[{idnr=FromDigits[Reverse[IntegerDigits[n]]]}, FromDigits[ Sort[ IntegerDigits[idnr+n]]]]; NestList[rats,6999,30] (* _Harvey P. Dale_, May 29 2014 *)

%o (Haskell)

%o a209879 n = a209879_list !! (n-1)

%o a209879_list = iterate a036839 6999

%Y Cf. A004000, A066710, A209878, A066711, A209880.

%K nonn,base

%O 1,1

%A _Reinhard Zumkeller_, Mar 14 2012