A072138 - OEIS

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A072138

Smallest k whose 'Reverse and Subtract' trajectory has a preperiodic part of length n.

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

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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

Table of n, a(n) for n=0..35.

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: A167788 A341012 A072968 * A109891 A104869 A104868

Adjacent sequences: A072135 A072136 A072137 * A072139 A072140 A072141

KEYWORD

base,nonn

AUTHOR

Klaus Brockhaus, Jun 24 2002

STATUS

approved