A072719 Numbers n such that 17 applications of 'Reverse and Subtract' lead to n, whereas fewer than 17 applications do not lead to n.

1186781188132188, 1464465185355348, 2178772178212278, 2191191178088088, 2196702178032978, 2202202177977978, 2334334176656658, 3041250269587497, 4361064356389356, 4906609350933906, 6232232537677674, 6543356534566434

Offset: 1

Author

Klaus Brockhaus, Jul 15 2002

Keywords

• base
• nonn

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.

All terms are divisible by 1099999989. - Hugo Pfoertner, Sep 23 2020

Examples

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

Links

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

Crossrefs

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

Formula

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