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A209879
RATS: Reverse Add Then Sort the digits applied to previous term, starting with 6999.
7
6999, 15699, 11355, 66666, 123333, 445566, 111111, 222222, 444444, 888888, 1677777, 3455589, 11112333, 33444444, 77778888, 156666666, 123333378, 666669999, 1356666666, 123333789, 11111667, 22777788, 11115555, 66666666, 123333333, 445566666, 111122223
OFFSET
1,1
COMMENTS
A114615(1) = 6999 is the smallest starting number for a RATS trajectory leading to a cycle of length 14: A114611(6999) = 14;
a(n + 14) = a(n) for n > 25.
LINKS
Eric Weisstein's World of Mathematics, RATS Sequence
Index entries for linear recurrences with constant coefficients, signature (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1).
FORMULA
a(n + 1) = A036839(a(n)).
MATHEMATICA
rats[n_]:=Module[{idnr=FromDigits[Reverse[IntegerDigits[n]]]}, FromDigits[ Sort[ IntegerDigits[idnr+n]]]]; NestList[rats, 6999, 30] (* Harvey P. Dale, May 29 2014 *)
PROG
(Haskell)
a209879 n = a209879_list !! (n-1)
a209879_list = iterate a036839 6999
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Reinhard Zumkeller, Mar 14 2012
STATUS
approved