A087999 - OEIS

A087999

a(n) is the LCM of palindromic divisors of n.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 1, 14, 15, 8, 1, 18, 1, 20, 21, 22, 1, 24, 5, 2, 9, 28, 1, 30, 1, 8, 33, 2, 35, 36, 1, 2, 3, 40, 1, 42, 1, 44, 45, 2, 1, 24, 7, 10, 3, 4, 1, 18, 55, 56, 3, 2, 1, 60, 1, 2, 63, 8, 5, 66, 1, 4, 3, 70, 1, 72, 1, 2, 15, 4, 77, 6, 1, 40, 9, 2, 1, 84, 5, 2, 3, 88

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OFFSET

1,2

COMMENTS

Sequence is not multiplicative. For example, a(141) = 141 != a(3)*a(47) = 3 * 1. - Franklin T. Adams-Watters, Oct 27 2006

LINKS

Indranil Ghosh, Table of n, a(n) for n = 1..50000

FORMULA

a(n)=1 for non-palindromic primes like 13.

EXAMPLE

n=252: a(252)=252=n,since palindromic divisors = {1,2,3,4,6,7,9,252};

n=255: a(255)=15<n, palind.div ={1,3,5}.

MATHEMATICA

Table[LCM @@ Select[Divisors[k], Reverse[x = IntegerDigits[#]] == x &], {k, 88}] (* Jayanta Basu, Aug 12 2013 *)

PROG

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

a(n) = lcm(select(x->ispal(x), divisors(n))); \\ Michel Marcus, Mar 27 2020

CROSSREFS

Cf. A087990.

Sequence in context: A034326 A053833 A167973 * A106614 A297242 A043272

Adjacent sequences: A087996 A087997 A087998 * A088000 A088001 A088002

KEYWORD

base,nonn

AUTHOR

Labos Elemer, Oct 14 2003

STATUS

approved