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A030547 Number of terms (including the initial term) needed to reach a palindrome when the Reverse Then Add! map (x -> x + (x-with-digits-reversed)) is repeatedly applied to n, or -1 if a palindrome is never reached. 2
1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 1, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 1, 2, 2, 2, 3, 2, 3, 2, 2, 2, 2, 1, 2, 3, 2, 3, 3, 2, 2, 2, 2, 2, 1, 2, 3, 3, 4, 2, 2, 2, 2, 3, 2, 1, 3, 4, 5, 2, 2, 2, 3, 2, 3, 3, 1, 5, 7, 2, 2, 3, 2, 3, 3, 4, 5, 1, 25, 2, 3, 2, 3, 3, 4, 5, 7, 25 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,10

COMMENTS

It is conjectured that a(196) is the smallest term equal to -1. See A023108.

REFERENCES

Daniel Lignon, Dictionnaire de (presque) tous les nombres entiers, Ellipses, Paris, 2012, 702 pages. See Entry 196.

LINKS

Table of n, a(n) for n=1..98.

Eric Weisstein's World of Mathematics, 196 Algorithm.

MATHEMATICA

Table[Length@

  NestWhileList[# + IntegerReverse[#] &, n, ! PalindromeQ[#]  &], {n, 98}] (* Robert Price, Oct 18 2019 *)

CROSSREFS

Cf. A006960, A023108, A063018, etc.

Equals A033665(n) + 1.

Sequence in context: A028950 A094916 A036485 * A254690 A156642 A155124

Adjacent sequences:  A030544 A030545 A030546 * A030548 A030549 A030550

KEYWORD

nonn,base

AUTHOR

Eric W. Weisstein

EXTENSIONS

Edited by N. J. A. Sloane, May 09 2015

STATUS

approved

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Last modified December 15 00:30 EST 2019. Contains 329988 sequences. (Running on oeis4.)