A144766 Terms in A144719 that are themselves decimal palindromes.

121, 10001, 10201, 36763, 1226221, 7673767, 12467976421, 1030507050301, 1120237320211, 1225559555221, 1234469644321, 1334459544331, 100330272033001, 100827848728001, 101222252222101, 103023070320301, 121363494363121, 134312696213431, 10022212521222001

Offset

1,1

Comments

Presumed infinite, but it is difficult to find more terms.

The earlier claim that this sequence is a subsequence of A046450 was incorrect, as the counterexample of 7673767 =97*79111 shows. The reason is that A046450 checks only concatenations in the natural order of the prime factors, but this sequence here allows for both orders, 97//79111 as well as 79111//97, to be palindromic. - R. J. Mathar, Jan 22 2009

3*10^14 < a(19) <= 10022212521222001. - Donovan Johnson, Dec 08 2010

Links

Giovanni Resta, Table of n, a(n) for n = 1..41

Formula

Subsequence of (A144719 INTERSECT A046328). - R. J. Mathar, Jan 22 2009

Example

10001 = 73 * 137; 73137 is a palindrome.

Crossrefs

Cf. A002113, A046450, A144719.

Sequence in context: A018849 A011814 A238320 * A277946 A263610 A176923

Adjacent sequences: A144763 A144764 A144765 * A144767 A144768 A144769

Keyword

base,hard,nonn

Author

Reikku Kulon, Sep 20 2008

Extensions

a(7)-a(18) from Donovan Johnson, Dec 08 2010

a(19) from Giovanni Resta, Aug 31 2018

Status

approved