OFFSET
1,1
COMMENTS
There are 22 twelve-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
All terms are divisible by 10999989. - Hugo Pfoertner, Sep 23 2020
LINKS
Ray Chandler, Table of n, a(n) for n = 1..22
FORMULA
n = f^22(n), n <> f^k(n) for k < 22, where f: x -> |x - reverse(x)|.
EXAMPLE
108811891188 -> 772386227613 -> 455663544336 -> 177781822218 -> 634446365553 -> 278882721117 -> 432244567755 -> 125520874479 -> 848957151042 -> 608805391194 -> 117611882388 -> 765676234323 -> 442243557756 -> 215511784488 -> 668975331024 -> 248841751158 -> 602315397684 -> 115521884478 -> 758966241033 -> 428823571176 -> 242351757648 -> 604405395594 -> 108811891188.
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Klaus Brockhaus, Jun 24 2002
STATUS
approved