A334392 - OEIS

A334392

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

16, 25, 26, 27, 32, 34, 38, 39, 46, 48, 49, 50, 51, 52, 54, 57, 58, 62, 64, 65, 68, 69, 74, 75, 76, 78, 80, 81, 82, 85, 86, 87, 91, 92, 93, 94, 95, 96, 98, 100, 102, 104, 106, 108, 112, 114, 115, 116, 117, 118, 119, 122, 123, 124, 125, 128, 129, 130, 133, 134

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OFFSET

1,1

COMMENTS

A334139, A334391 and this sequence form a partition of the set of positive integers N* (A000027).

The integers {2^k, k >= 4, 2^k non-palindrome} form a subsequence whose first few terms are : 16, 32, 64, 128, ...

LINKS

Table of n, a(n) for n=1..60.

Wikipedia, Partition of a set

EXAMPLE

50 has 3 palindromic divisors {1, 2, 5} then A087999(50) = 10 and 50 is a term.

MATHEMATICA

Select[Range[125], !MemberQ[{1, #}, LCM @@ Select[Divisors[#], PalindromeQ]] &] (* Amiram Eldar, May 05 2020 *)

PROG

(PARI) ispal(x) = my(d=digits(x)); d == Vecrev(d);

isok(m) = my(d=divisors(m), lcmpd = lcm(select(x->ispal(x), d))); (lcmpd != 1) && (lcmpd != m); \\ Michel Marcus, May 05 2020

CROSSREFS

Cf. A087990, A087999.

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].

Sequence in context: A170985 A202335 A071524 * A227651 A348320 A095409

Adjacent sequences: A334389 A334390 A334391 * A334393 A334394 A334395

KEYWORD

nonn,base

AUTHOR

Bernard Schott, May 04 2020

STATUS

approved