A087997 a(n) is the least number with n palindromic divisors.

1, 2, 4, 6, 12, 24, 72, 66, 484, 132, 616, 264, 2112, 792, 1848, 2772, 7326, 8712, 5544, 13332, 14652, 24024, 36036, 26664, 87912, 102564, 72072, 79992, 186648, 205128, 360360, 279972, 264264, 666666, 1213212, 879912, 559944, 888888, 792792

Offset

1,2

Links

Donovan Johnson, Table of n, a(n) for n = 1..150

Formula

a(n)=Min{x; A087990[x]=n}

Example

n=24: a(24)=26664 has 32 divisors of which 24 are palindromic numbers: {1, 2, 3, 4, 6, 8, 11, 22, 33, 44, 66, 88, 101, 202, 303, 404, 606, 808, 1111, 2222, 3333, 4444, 6666, 8888}.
Some solutions are palindromic (like 2112), some are not (like 132).

Mathematica

t = Table[Count[Divisors[k], _?(Reverse[x = IntegerDigits[#]] == x &)], {k, 2, 15*10^5, 2}]; Join[{1}, Table[i = 1; While[t[[i]] != k, i++]; 2 i, {k, 2, 39}]] (* Jayanta Basu, Aug 12 2013 *)
Module[{pds=Table[{n, Count[Divisors[n], _?PalindromeQ]}, {n, 1214000}]}, Table[ SelectFirst[pds, #[[2]]==k&], {k, 39}]][[All, 1]] (* Harvey P. Dale, Dec 17 2021 *)

Crossrefs

Cf. A087990.

Sequence in context: A337993 A093036 A340548 * A355699 A340638 A177905

Adjacent sequences: A087994 A087995 A087996 * A087998 A087999 A088000

Keyword

base,nonn

Author

Labos Elemer, Oct 13 2003

Extensions

More terms from Ray Chandler, Oct 17 2003

Status

approved