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 A072138 Smallest k whose 'Reverse and Subtract' trajectory has a preperiodic part of length n. 2
 0, 1, 10, 16, 14, 15, 13, 1011, 1017, 1037, 1027, 1014, 1013, 1028, 100113, 100104, 100145, 100134, 100103, 100112, 100133, 100187, 100114, 100128, 100194, 100107, 100307, 100277, 100413, 100345, 100429, 100215, 100427, 100214, 100433, 100335 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS 'Reverse and Subtract' (cf. A072137) is defined by x -> |x - reverse(x)|. For small n the last term of the preperiodic part of the trajectory (cf. A072139) is a palindrome, so this sequence is a weak analog of A033665, which uses 'Reverse and Add'. - 1012 is the first n such that last term of the preperiodic part is not palindromic (cf. A072140). LINKS EXAMPLE a(8) = 1017, since 1017 is the smallest number whose 'Reverse and Subtract' trajectory has eight preperiodic terms: 1017 -> 6084 -> 1278 -> 7443 -> 3996 -> 2997 -> 4995 -> 999. CROSSREFS Cf. A033665, A072137, A072139, A072140, A072146. Sequence in context: A175335 A167788 A072968 * A109891 A104869 A104868 Adjacent sequences:  A072135 A072136 A072137 * A072139 A072140 A072141 KEYWORD base,nonn AUTHOR Klaus Brockhaus, Jun 24 2002 STATUS approved

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Last modified July 20 22:20 EDT 2019. Contains 325189 sequences. (Running on oeis4.)