login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

Nonpalindromic integers with palindromic product of divisors.
0

%I #40 Sep 04 2019 08:11:41

%S 26,49,2285,1109111,3069307,12028229,12866669,110091011,10207355549,

%T 11010911011,11100910111,13579355059,30101273647,30693069307,

%U 111283619361

%N Nonpalindromic integers with palindromic product of divisors.

%C Many terms of A327325 are palindromes, hence this sequence.

%C Intersection of A029742 and A327325.

%C a(16) > 3.5*10^11. - _Giovanni Resta_, Sep 04 2019

%e Divisors of 26 are : 1,2,13,26 and 1*2*13*26=676.

%t Select[Range[3200000], !PalindromeQ[#] && PalindromeQ[#^(DivisorSigma[0, #]/2)] &] (* _Amiram Eldar_, Sep 02 2019 *)

%o (PARI) ispal(n) = my(d=digits(n)); d == Vecrev(d);

%o isok(n) = !ispal(n) && ispal(vecprod(divisors(n)));

%Y Cf. A002113, A007955, A029742, A327325.

%K nonn,base,more

%O 1,1

%A _Michel Marcus_, Sep 02 2019

%E a(8)-a(15) from _Giovanni Resta_, Sep 04 2019