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A072079
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Sum of 3-smooth divisors of n.
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2
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1, 3, 4, 7, 1, 12, 1, 15, 13, 3, 1, 28, 1, 3, 4, 31, 1, 39, 1, 7, 4, 3, 1, 60, 1, 3, 40, 7, 1, 12, 1, 63, 4, 3, 1, 91, 1, 3, 4, 15, 1, 12, 1, 7, 13, 3, 1, 124, 1, 3, 4, 7, 1, 120, 1, 15, 4, 3, 1, 28, 1, 3, 13, 127, 1, 12, 1, 7, 4, 3, 1, 195, 1, 3, 4, 7, 1, 12, 1, 31, 121
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OFFSET
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1,2
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COMMENTS
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a(n) = A000203(A065331(n)).
Multiplicative with a(2^e) = 2^(e+1)-1, a(3^e) = (3^(e+1)-1)/2, a(p^e) = 1, p>3. Christian G. Bower May 20, 2005.
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LINKS
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Amiram Eldar, Table of n, a(n) for n = 1..10000
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FORMULA
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a(n) = (2^(A007814(n)+1)-1)*(3^(A007949(n)+1)-1)/2.
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MATHEMATICA
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f[p_, e_] := If[p > 3, 1, (p^(e + 1) - 1)/(p - 1)]; a[1] = 1; a[n_] := Times @@ (f @@@ FactorInteger[n]); Array[a, 100] (* Amiram Eldar, Aug 29 2019 *)
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CROSSREFS
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Cf. A000203, A003586, A072078.
Sequence in context: A322017 A093087 A130893 * A116073 A166043 A294896
Adjacent sequences: A072076 A072077 A072078 * A072080 A072081 A072082
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KEYWORD
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nonn,mult
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AUTHOR
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Reinhard Zumkeller, Jun 13 2002
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STATUS
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approved
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