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A033865 Start with n; if palindrome, stop; otherwise add to itself with digits reversed; a(n) gives palindrome at which it stops, or -1 if no palindrome is ever reached. 43
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 11, 33, 44, 55, 66, 77, 88, 99, 121, 22, 33, 22, 55, 66, 77, 88, 99, 121, 121, 33, 44, 55, 33, 77, 88, 99, 121, 121, 363, 44, 55, 66, 77, 44, 99, 121, 121, 363, 484, 55, 66, 77, 88, 99, 55, 121, 363, 484, 1111, 66, 77, 88, 99, 121, 121, 66, 484, 1111, 4884, 77, 88, 99, 121, 121, 363, 484, 77, 4884, 44044, 88 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
COMMENTS
It is believed that a(196) = -1.
REFERENCES
M. Donner, I Love Me, Vol. I: S. Wordrow's palindromic encyclopedia (Algonquin Books, 1996) p. 268
LINKS
O. Forster, ARIBAS
Eric Weisstein's World of Mathematics, 196-Algorithm.
EXAMPLE
19 -> 19 + 91 = 110 -> 110 + 011 = 121, so a(19) = 121.
MATHEMATICA
Table[NestWhile[# + FromDigits[Reverse[IntegerDigits[#]]] &, n, IntegerDigits[#] != Reverse[IntegerDigits[#]] &], {n, 0, 90}] (* Harvey P. Dale, Dec 18 2011 *)
PROG
(ARIBAS): var st: stack; end; for k := 0 to 60 do n := k; while n <> int_reverse(n) do n := n + int_reverse(n); end; stack_push(st, n); end; stack2array(st).
(PARI) a(n)=my(k); while((k=fromdigits(Vecrev(digits(n)))) != n, n += k); n \\ infinite loop if a(n) = -1; Charles R Greathouse IV, Dec 13 2015
CROSSREFS
Cf. A061563, A016016, A023109, A006960, A023108, A002113, A033665 (number of steps).
Sequence in context: A082273 A256755 A045876 * A364274 A118764 A226134
KEYWORD
nonn,base,nice
AUTHOR
EXTENSIONS
More terms from Jenise Smalley (neicey01(AT)hotmail.com), Oct 18 2001
STATUS
approved

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Last modified March 19 01:34 EDT 2024. Contains 370952 sequences. (Running on oeis4.)