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A087997
a(n) is the least number with n palindromic divisors.
12
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
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
KEYWORD
base,nonn
AUTHOR
Labos Elemer, Oct 13 2003
EXTENSIONS
More terms from Ray Chandler, Oct 17 2003
STATUS
approved