A061563 Start with n; add to itself with digits reversed; if palindrome, stop; otherwise repeat; a(n) gives palindrome at which it stops, or -1 if no palindrome is ever reached.

0, 2, 4, 6, 8, 11, 33, 55, 77, 99, 11, 22, 33, 44, 55, 66, 77, 88, 99, 121, 22, 33, 44, 55, 66, 77, 88, 99, 121, 121, 33, 44, 55, 66, 77, 88, 99, 121, 121, 363, 44, 55, 66, 77, 88, 99, 121, 121, 363, 484, 55, 66, 77, 88, 99, 121, 121, 363, 484, 1111, 66, 77, 88, 99, 121

Offset

0,2

Comments

It is believed that n = 196 is the smallest integer which never reaches a palindrome.

Links

T. D. Noe, Table of n, a(n) for n=0..195

Index entries for sequences related to Reverse and Add!

Example

19 -> 19 + 91 = 110 -> 110 + 011 = 121, so a(19) = 121.

Mathematica

tol = 1000; r[n_] := FromDigits[Reverse[IntegerDigits[n]]]; palQ[n_] := n == r[n]; ar[n_] := n + r[n]; Table[k = 0; If[palQ[n], n = ar[n]; k = 1]; While[! palQ[n] && k < tol, n = ar[n]; k++]; If[k == tol, n = -1]; n, {n, 0, 64}] (* Jayanta Basu, Jul 11 2013 *)
Table[Module[{k=n+IntegerReverse[n]}, While[k!=IntegerReverse[k], k=k+IntegerReverse[k]]; k], {n, 0, 70}] (* The program uses the IntegerReverse function from Mathematica version 10 *) (* Harvey P. Dale, Jul 19 2016 *)

Prog

(ARIBAS): var st: stack; test: boolean; end; for k := 0 to 60 do n := k; test := true; while test do n := n + int_reverse(n); test := n <> int_reverse(n); end; stack_push(st, n); end; stack2array(st).

Crossrefs

Cf. A033865. A016016 (number of steps), A023109, A006950, A023108.

Sequence in context: A332240 A068062 A088169 * A345113 A099994 A068065

Adjacent sequences: A061560 A061561 A061562 * A061564 A061565 A061566

Keyword

nonn,base,easy,nice,look

Author

N. J. A. Sloane, May 18 2001

Extensions

Corrected and extended by Klaus Brockhaus, May 20 2001

More terms from Ray Chandler, Jul 25 2003

Status

approved