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.

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

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: A094916 A036485 A331971 * A339932 A254690 A156642

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