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A033665 Number of 'Reverse and Add' steps needed to reach a palindrome, or -1 if never reaches a palindrome. +0
13
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 0, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 0, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 0, 1, 2, 1, 2, 2, 1, 1, 1, 1, 1, 0, 1, 2, 2, 3, 1, 1, 1, 1, 2, 1, 0, 2, 3, 4, 1, 1, 1, 2, 1, 2, 2, 0, 4, 6, 1, 1, 2, 1, 2, 2, 3, 4, 0, 24, 1, 2, 1, 2, 2, 3, 4, 6, 24, 0, 1, 0, 1, 1 (list; graph; listen)
OFFSET

0,20

COMMENT

Palindromes themselves are not 'Reverse and Add!'ed, so they yield a zero !

REFERENCES

D. Wells, The Penguin Dictionary of Curious and Interesting Numbers, pp. 142-3 Penguin Books 1987.

LINKS

P. De Geest, Some thematic websources

Jason Doucette, World Records

S. K. Eddins, The Palindromic Order Of A Number

I. Peter, More trajectories

T. Trotter, Jr., Palindrome Power

Index entries for sequences related to Reverse and Add!

EXAMPLE

19 -> 19+91=110 -> 110+011 = 110+11 = 121 = palindrome, took 2 steps, so a(19)=2.

CROSSREFS

Cf. A023109, A006960, A016016, A023109, A006960.

Sequence in context: A005090 A073490 A135341 this_sequence A104234 A037870 A026920

Adjacent sequences: A033662 A033663 A033664 this_sequence A033666 A033667 A033668

KEYWORD

nonn,base,easy

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com).

EXTENSIONS

More terms from Patrick De Geest (pdg(AT)worldofnumbers.com), Jun 15 1998.

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Last modified November 29 12:46 EST 2009. Contains 167659 sequences.


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