A152235 - OEIS

A152235

Largest squarefree number dividing the number of divisors n.

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, 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, 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

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OFFSET

1,2

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

Index entries for sequences computed from exponents in factorization of n

FORMULA

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

MATHEMATICA

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

PROG

(Magma) [ 1 ] cat [ &*[ k[1]: k in Factorization(NumberOfDivisors(n)) ]: n in [2..105] ]; // Klaus Brockhaus, Dec 03 2008