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 A072718 Numbers n such that 12 applications of 'Reverse and Subtract' lead to n, whereas fewer than 12 applications do not lead to n. 17
 118722683079, 138346366158, 178574614218, 277673713317, 316920881277, 336544564356, 435643663455, 455267148336, 614218178574, 633841861653, 713317277673, 851663544732 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS There are 12 twelve-digit terms in the sequence. Further terms are obtained (a) by inserting at the center of these terms either any number of 0's (for 178574614218, 277673713317, 614218178574, 713317277673) or any number of 9's (for the other eight terms) 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. LINKS FORMULA n = f^12(n), n <> f^k(n) for k < 12, where f: x -> |x - reverse(x)|. EXAMPLE 118722683079 -> 851663544732 -> 614218178574 -> 138346366158 -> 713317277673 -> 336544564356 -> 316920881277 -> 455267148336-> 178574614218-> 633841861653-> 277673713317-> 435643663455-> 118722683079. CROSSREFS Cf. A072137, A072141, A072142, A072143, A072719. Sequence in context: A287233 A122717 A287238 * A034652 A015402 A108389 Adjacent sequences:  A072715 A072716 A072717 * A072719 A072720 A072721 KEYWORD base,nonn AUTHOR Klaus Brockhaus, Jul 15 2002 STATUS approved

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Last modified October 20 10:45 EDT 2019. Contains 328257 sequences. (Running on oeis4.)