|
|
A261245
|
|
The 21 palindromic divisors of the palindrome 12345678987654321.
|
|
1
|
|
|
1, 3, 9, 111, 333, 999, 12321, 36963, 1001001, 3003003, 9009009, 111111111, 333333333, 999999999, 12333333321, 36999999963, 1002003002001, 3006009006003, 111222333222111, 333666999666333, 12345678987654321
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
There are 45 divisors of 12345678987654321.
Motivated by A261072 by Ilya Gutkovskiy, which has only six palindromic divisors, namely 1, 3, 7, 9, 171, 1234567890987654321.
12345678987654321 = A002275(9)^2 = 111111111^2 (observed by Jon E. Schoenfield). The repunit R(9) has the eight palindromic divisors 1, 3, 9, 111, 333, 1001001, 3003003, 111111111.
All entries a(n) can be obtained by multiplying two palindromic divisors of R(9).
|
|
LINKS
|
|
|
MATHEMATICA
|
Select[Divisors[12345678987654321], PalindromeQ] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, May 13 2019 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy,base,fini,full
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|