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A327498
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Maximum divisor of n whose prime multiplicities are distinct (A130091).
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42
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1, 2, 3, 4, 5, 3, 7, 8, 9, 5, 11, 12, 13, 7, 5, 16, 17, 18, 19, 20, 7, 11, 23, 24, 25, 13, 27, 28, 29, 5, 31, 32, 11, 17, 7, 18, 37, 19, 13, 40, 41, 7, 43, 44, 45, 23, 47, 48, 49, 50, 17, 52, 53, 54, 11, 56, 19, 29, 59, 20, 61, 31, 63, 64, 13, 11, 67, 68, 23
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OFFSET
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1,2
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COMMENTS
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A number's prime multiplicities are also called its (unsorted) prime signature.
Every positive integer appears a finite number of times in the sequence; a prime p occurs 2^(PrimePi(p) - 1) times. - David A. Corneth, Sep 17 2019
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LINKS
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FORMULA
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EXAMPLE
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The divisors of 60 whose prime multiplicities are distinct are {1, 2, 3, 4, 5, 12, 20}, so a(60) = 20, the largest of these divisors.
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MATHEMATICA
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Table[Max[Select[Divisors[n], UnsameQ@@Last/@FactorInteger[#]&]], {n, 100}]
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PROG
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(PARI) a(n) = {my(m = Map(), f = factor(n), res = 1); forstep(i = #f~, 1, -1, forstep(j = f[i, 2], 1, -1, if(!mapisdefined(m, j), mapput(m, j, j); res*=f[i, 1]^j; next(2)))); res} \\ David A. Corneth, Sep 17 2019
(PARI)
A351564(n) = issquarefree(factorback(apply(e->prime(e), (factor(n)[, 2]))));
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CROSSREFS
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See link for additional cross-references.
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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