This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A261072 #47 Feb 16 2025 08:33:26 %S A261072 1,3,7,9,19,21,57,63,133,171,399,1197,928163,2784489,6497141,8353467, %T A261072 17635097,19491423,52905291,58474269,123445679,158715873,370337037, %U A261072 1111011111,1111211111,3333633333,7778477777,10000899999,21113011109 %N A261072 Divisors of 1234567890987654321. %C A261072 1234567890987654321 = A057139(10) is a palindrome with 48 divisors. See the link with all divisors. %C A261072 From _Wolfdieter Lang_, Aug 22 2015: (Start) %C A261072 The palindromes of this sequence are 1, 3, 7, 9, 171, 1234567890987654321. %C A261072 1234567890987654321 = 1111011111 * 1111211111 (observed by _Jon E. Schoenfield_). %C A261072 The palindromic divisors of 1111011111 are 1, 3, 7, 9 and 171. The only palindromic divisor of 1111211111 is 1. Therefore, of the six palindromes of this sequence only 1234567890987654321 cannot be obtained from the product of the palindromic divisors of 1111011111 with those of 1111211111. (End) %H A261072 Ilya Gutkovskiy, <a href="/A261072/b261072.txt">Table of n, a(n) for n = 1..48</a> %H A261072 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Divisor.html">Divisor</a>. %H A261072 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PalindromicNumber.html">Palindromic Number</a>. %p A261072 numtheory[divisors](1234567890987654321); # _Wesley Ivan Hurt_, Aug 11 2015 %t A261072 Divisors[1234567890987654321] %o A261072 (Magma) [Divisors(1234567890987654321)]; // _Vincenzo Librandi_, Aug 09 2015 %o A261072 (PARI) divisors(1234567890987654321) \\ _Wesley Ivan Hurt_, Aug 11 2015 %Y A261072 Cf. A057139, A261245. %K A261072 nonn,easy,fini,full %O A261072 1,2 %A A261072 _Ilya Gutkovskiy_, Aug 08 2015