cp's OEIS Frontend

A334392 Numbers m such that the LCM of their palindromic divisors is neither 1 nor m.

%I A334392 #19 May 07 2020 08:49:06
%S A334392 16,25,26,27,32,34,38,39,46,48,49,50,51,52,54,57,58,62,64,65,68,69,74,
%T A334392 75,76,78,80,81,82,85,86,87,91,92,93,94,95,96,98,100,102,104,106,108,
%U A334392 112,114,115,116,117,118,119,122,123,124,125,128,129,130,133,134
%N A334392 Numbers m such that the LCM of their palindromic divisors is neither 1 nor m.
%C A334392 A334139, A334391 and this sequence form a partition of the set of positive integers N* (A000027).
%C A334392 The integers {2^k, k >= 4, 2^k non-palindrome} form a subsequence whose first few terms are : 16, 32, 64, 128, ...
%H A334392 Wikipedia, <a href="https://en.wikipedia.org/wiki/Partition_of_a_set">Partition of a set</a>
%e A334392 50 has 3 palindromic divisors {1, 2, 5} then A087999(50) = 10 and 50 is a term.
%t A334392 Select[Range[125], !MemberQ[{1, #}, LCM @@ Select[Divisors[#], PalindromeQ]] &] (* _Amiram Eldar_, May 05 2020 *)
%o A334392 (PARI) ispal(x) = my(d=digits(x)); d == Vecrev(d);
%o A334392 isok(m) = my(d=divisors(m), lcmpd = lcm(select(x->ispal(x), d))); (lcmpd != 1) && (lcmpd != m); \\ _Michel Marcus_, May 05 2020
%Y A334392 Cf. A087990, A087999.
%Y A334392 Cf. A334391 [LCM(palindromic divisors of m) = 1], A334139 [LCM(palindromic divisors of m) = m], this sequence [LCM(palindromic divisors of m) != 1 and != m].
%K A334392 nonn,base
%O A334392 1,1
%A A334392 _Bernard Schott_, May 04 2020