A261912 Numbers with palindromic order 5.

101073, 101082, 101100, 101155, 101199, 102192, 102299, 103275, 103293, 103366, 103399, 103502, 104332, 104342, 104352, 104362, 104372, 104382, 104392, 104499, 104602, 105432, 105442, 105452, 105462, 105472, 105482, 105492, 105493, 105544, 105577, 105599, 105702

Offset

1,1

Comments

See A261913 for definition.

In the Friedman Problem of the Month page, there is a statement by John Hoffman which, if I have interpreted it correctly, asserts that this sequence has only a finite number of terms. However, Chai Wah Wu has extended the sequence out to 10^8, finding 481384 terms, the last one being a(481384) = 99998180. This sequence does not appear to be finite.

The first terms of this sequence are just beyond A109326(5). It can be expected that at least beyond A109326(6) = 1000101024 there will be examples where N-prevpal(N) and N-prevpal(prevpal(N)) are both of order 5; these numbers could be termed to be of order 6, and so on. - M. F. Hasler, Sep 13 2015

Links

Chai Wah Wu, Table of n, a(n) for n = 1..2278

Erich Friedman, Problem of the Month (June 1999)

M. F. Hasler, Sum of palindromes, OEIS wiki, Sep 10 2015

Chai Wah Wu, Table of n, a(n) for n = 1..481384 (zipped file)

Crossrefs

Cf. A002113, A261907, A261910, A261911, A261913, A262528.

Sequence in context: A043642 A122233 A122243 * A122236 A122246 A210895

Adjacent sequences: A261909 A261910 A261911 * A261913 A261914 A261915

Keyword

nonn,base

Author

N. J. A. Sloane, Sep 10 2015

Extensions

More terms from Chai Wah Wu, Sep 11 2015 and Sep 12 2015

Status

approved