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A132740
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Largest divisor of n coprime to 10.
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10
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1, 1, 3, 1, 1, 3, 7, 1, 9, 1, 11, 3, 13, 7, 3, 1, 17, 9, 19, 1, 21, 11, 23, 3, 1, 13, 27, 7, 29, 3, 31, 1, 33, 17, 7, 9, 37, 19, 39, 1, 41, 21, 43, 11, 9, 23, 47, 3, 49, 1, 51, 13, 53, 27, 11, 7, 57, 29, 59, 3, 61, 31, 63, 1, 13, 33, 67, 17, 69, 7, 71, 9, 73, 37, 3, 19, 77, 39, 79, 1, 81
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| a(n) = A000265(A132739(n)) = A132739(A000265(n));
a(n) = n / A132741(n);
A051626(a(n)) = A051626(n); A007732(a(n)) = A007732(n);
a(A003592(n)) = 1.
Multiplicative with a(2^e)=1, a(5^e)=1 and a(p^e) = p^e for p=3 and p>=7.
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LINKS
| R. Zumkeller, Table of n, a(n) for n = 1..10000
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FORMULA
| Dirichlet g.f. zeta(s-1)*(2^s-2)*(5^s-5)/((2^s-1)*(5^s-1)). - R. J. Mathar, Sep 06 2011
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EXAMPLE
| a(1050) = a(2*3*5*5*7) = 3*7 = 21.
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MAPLE
| A132740 := proc(n) n/A132741(n) ; end proc: # R. J. Mathar, Sep 06 2011
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MATHEMATICA
| a[n_] := FixedPoint[ Quotient[#, GCD[#, 10]]& , n]; Table[a[n], {n, 1, 81}](* From Jean-François Alcover, Sep 06 2011, after V. Orlovsky *)
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PROG
| (Haskell)
a132740 = a132739 . a000265 -- Reinhard Zumkeller, Apr 08 2011
(PARI) a(n)=n/5^valuation(n, 5)>>valuation(n, 2) \\ Charles R Greathouse IV, Sep 06 2011
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CROSSREFS
| Sequence in context: A170819 A140211 A097706 * A106621 A011085 A199922
Adjacent sequences: A132737 A132738 A132739 * A132741 A132742 A132743
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KEYWORD
| nonn,mult,easy
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AUTHOR
| Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Aug 27 2007
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