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A087997 a(n) is the least number with n palindromic divisors. 12

%I #20 Mar 04 2022 14:18:49

%S 1,2,4,6,12,24,72,66,484,132,616,264,2112,792,1848,2772,7326,8712,

%T 5544,13332,14652,24024,36036,26664,87912,102564,72072,79992,186648,

%U 205128,360360,279972,264264,666666,1213212,879912,559944,888888,792792

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

%H Donovan Johnson, <a href="/A087997/b087997.txt">Table of n, a(n) for n = 1..150</a>

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

%e 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}.

%e Some solutions are palindromic (like 2112), some are not (like 132).

%t 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 *)

%t 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 *)

%Y Cf. A087990.

%K base,nonn

%O 1,2

%A _Labos Elemer_, Oct 13 2003

%E More terms from _Ray Chandler_, Oct 17 2003

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Last modified March 29 10:44 EDT 2024. Contains 371268 sequences. (Running on oeis4.)