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A072719 Numbers n such that 17 applications of 'Reverse and Subtract' lead to n, whereas fewer than 17 applications do not lead to n. 18
1186781188132188, 1464465185355348, 2178772178212278, 2191191178088088, 2196702178032978, 2202202177977978, 2334334176656658, 3041250269587497, 4361064356389356, 4906609350933906, 6232232537677674, 6543356534566434 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

There are 17 sixteen-digit terms in the sequence. Further terms are obtained (a) by inserting at the center of these terms any number of 9's and (b) by concatenating a term any number of times with itself and inserting an equal number of 0's at all junctures. Method (b) may be applied recursively to all terms. - Revised thanks to a comment from Hans Havermann, Jan 27 2004.

This is a working sequence. It is neither by computation nor by proof guaranteed that there are no smaller or interleaved terms.

LINKS

Ray Chandler, Table of n, a(n) for n = 1..17

FORMULA

n = f^17(n), n <> f^k(n) for k < 17, where f: x -> |x - reverse(x)|.

EXAMPLE

1186781188132188 -> 7625537623744623 -> 4361064356389356 -> 2178772178212278 -> 6543356534566434 -> 2196702178032978 -> 6595606534043934 -> 2202202177977978 -> 6595595534044044 -> 2191191178088088 -> 6617617533823824 -> 2334334176656658 ->  6232232537677674 -> 1464465185355348 -> 6971070630289293 -> 3041250269587497 -> 4906609350933906 -> 1186781188132188.

CROSSREFS

Cf. A072137, A072141, A072142, A072143, A072718.

Sequence in context: A235167 A095431 A282672 * A185433 A134692 A288286

Adjacent sequences:  A072716 A072717 A072718 * A072720 A072721 A072722

KEYWORD

base,nonn

AUTHOR

Klaus Brockhaus, Jul 15 2002

STATUS

approved

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Last modified October 19 03:34 EDT 2019. Contains 328211 sequences. (Running on oeis4.)