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A157721
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a(n) = 0 if n is 1 or a prime, otherwise a(n) = product of composite (nonprime) divisors of n.
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0
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0, 0, 0, 4, 0, 6, 0, 32, 9, 10, 0, 288, 0, 14, 15, 512, 0, 972, 0, 800, 21, 22, 0, 55296, 25, 26, 243, 1568, 0, 27000, 0, 16384, 33, 34, 35, 1679616, 0, 38, 39, 256000, 0, 74088, 0, 3872, 6075, 46, 0, 42467328, 49, 12500, 51, 5408, 0, 1417176, 55, 702464, 57, 58, 0
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OFFSET
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1,4
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COMMENTS
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LINKS
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EXAMPLE
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a(12) = 4*6*12 = 288, composite divisors = {4,6,12}.
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MATHEMATICA
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f[n_] := If[n == 1 || PrimeQ@n, 0, Times @@ Select[Divisors@n, ! PrimeQ@# &]]; Array[f, 60] (* Robert G. Wilson v, May 04 2009 *)
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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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