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A033665
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Number of 'Reverse and Add' steps needed to reach a palindrome, or -1 if never reaches a palindrome.
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14
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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; refs; listen; history; internal format)
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OFFSET
| 0,20
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COMMENTS
| Palindromes themselves are not 'Reverse and Add!'ed, so they yield a zero !
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REFERENCES
| D. Wells, The Penguin Dictionary of Curious and Interesting Numbers, pp. 142-3 Penguin Books 1987.
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LINKS
| Kerry Mitchell, Table of n, a(n) for n = 0..10000
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!
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EXAMPLE
| 19 -> 19+91=110 -> 110+011 = 110+11 = 121 = palindrome, took 2 steps, so a(19)=2.
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CROSSREFS
| Cf. A023109, A006960, A016016, A023109, A006960.
Sequence in context: A073490 A194285 A135341 * A104234 A037870 A206588
Adjacent sequences: A033662 A033663 A033664 * A033666 A033667 A033668
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KEYWORD
| nonn,base,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from Patrick De Geest (pdg(AT)worldofnumbers.com), Jun 15 1998.
Numbers n such that a(n) is given as -1 apparently do not lead to palindromes, but that has not yet been proved.
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