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A124675
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a(n) = product of the positive integers k, k<= n, such that the positive integers <= k and coprime to k are also coprime to n.
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0
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1, 2, 6, 8, 120, 12, 5040, 384, 324, 80, 39916800, 144, 6227020800, 672, 90, 10321920, 355687428096000, 2592, 121645100408832000, 1600, 756, 84480, 25852016738884976640000, 62208, 9000000, 1198080, 14285134080, 18816
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OFFSET
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1,2
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LINKS
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EXAMPLE
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The positive integers k, k <= 6, where the positive integers <= k and coprime to k are also coprime to 6, are 1,2,6. So a(6) = 1*2*6 = 12.
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MATHEMATICA
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f[n_] := Select[Range[n], GCD[ #, n] == 1 &]; g[n_] := Select[Range[n], Times @@ GCD[f[ # ], n] == 1 &]; Times @@@ Table[g[n], {n, 30}] (* Ray Chandler, Dec 24 2006 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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