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A152235 Largest squarefree number dividing the number of divisors n. 3
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 (list; graph; refs; listen; history; text; internal format)
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

(PARI) for(n=1, 50, print1(factorback(factorint(numdiv(n))[, 1]), ", ")) \\ G. C. Greubel, Jul 13 2017; corrected by Amiram Eldar, Sep 01 2019 *)

CROSSREFS

Cf. A000005, A007947.

Sequence in context: A071188 A078545 A163105 * A278966 A123582 A214861

Adjacent sequences:  A152232 A152233 A152234 * A152236 A152237 A152238

KEYWORD

easy,nonn

AUTHOR

Giovanni Teofilatto, Nov 30 2008

EXTENSIONS

Extended by Klaus Brockhaus, Dec 03 2008

STATUS

approved

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Last modified November 19 19:09 EST 2019. Contains 329323 sequences. (Running on oeis4.)