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.
All terms are divisible by 1099999989. - Hugo Pfoertner, Sep 23 2020
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
KEYWORD
base,nonn
AUTHOR
Klaus Brockhaus, Jul 15 2002
STATUS
approved