A072143 Numbers n such that 22 applications of 'Reverse and Subtract' lead to n, whereas fewer than 22 applications do not lead to n.

108811891188, 115521884478, 117611882388, 125520874479, 177781822218, 215511784488, 242351757648, 248841751158, 278882721117, 428823571176, 432244567755, 442243557756, 455663544336, 602315397684, 604405395594

Offset: 1

Author

Klaus Brockhaus, Jun 24 2002

Keywords

• base
• nonn

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

Examples

			108811891188 -> 772386227613 -> 455663544336 -> 177781822218 -> 634446365553 -> 278882721117 -> 432244567755 -> 125520874479 -> 848957151042 -> 608805391194 -> 117611882388 -> 765676234323 -> 442243557756 -> 215511784488 -> 668975331024 -> 248841751158 -> 602315397684 -> 115521884478 -> 758966241033 -> 428823571176 -> 242351757648 -> 604405395594 -> 108811891188.
		

Links

• Ray Chandler, Table of n, a(n) for n = 1..22

Crossrefs

Cf. A072137, A072140, A072141, A072142, A072718, A072719.

Formula

n = f^22(n), n <> f^k(n) for k < 22, where f: x -> |x - reverse(x)|.