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

1,1

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

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

Sequence in context: A344751 A221286 A074337 * A233495 A233616 A095427

Adjacent sequences: A072140 A072141 A072142 * A072144 A072145 A072146

Keyword

base,nonn

Author

Klaus Brockhaus, Jun 24 2002

Status

approved