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A152235 Largest squarefree number dividing the number of divisors n. 3

%I

%S 1,2,2,3,2,2,2,2,3,2,2,6,2,2,2,5,2,6,2,6,2,2,2,2,3,2,2,6,2,2,2,6,2,2,

%T 2,3,2,2,2,2,2,2,2,6,6,2,2,10,3,6,2,6,2,2,2,2,2,2,2,6,2,2,6,7,2,2,2,6,

%U 2,2,2,6,2,2,6,6,2,2,2,10,5,2,2,6,2,2,2,2,2,6,2,6,2,2,2,6,2,6,6,3,2,2,2,2,2

%N Largest squarefree number dividing the number of divisors n.

%H Antti Karttunen, <a href="/A152235/b152235.txt">Table of n, a(n) for n = 1..10000</a>

%H <a href="/index/Eu#epf">Index entries for sequences computed from exponents in factorization of n</a>

%F a(n) = rad(tau(n)) = A007947(A000005(n)).

%t f[n_] := Last@ Select[ Divisors@ DivisorSigma[0, n], SquareFreeQ@# &]; Array[f, 105] (* _Robert G. Wilson v_, Dec 23 2008 *)

%o (MAGMA) [ 1 ] cat [ &*[ k[1]: k in Factorization(NumberOfDivisors(n)) ]: n in [2..105] ]; // _Klaus Brockhaus_, Dec 03 2008

%o (PARI) for(n=1,50, print1(factorback(factorint(numdiv(n))[,1]), ", ")) \\ _G. C. Greubel_, Jul 13 2017; corrected by _Amiram Eldar_, Sep 01 2019 *)

%Y Cf. A000005, A007947.

%K easy,nonn

%O 1,2

%A _Giovanni Teofilatto_, Nov 30 2008

%E Extended by _Klaus Brockhaus_, Dec 03 2008

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Last modified December 8 09:32 EST 2019. Contains 329862 sequences. (Running on oeis4.)