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A323600
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Dirichlet convolution of sigma with omega.
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2
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0, 1, 1, 4, 1, 9, 1, 11, 5, 11, 1, 31, 1, 13, 12, 26, 1, 38, 1, 39, 14, 17, 1, 81, 7, 19, 18, 47, 1, 83, 1, 57, 18, 23, 16, 127, 1, 25, 20, 103, 1, 101, 1, 63, 53, 29, 1, 187, 9, 66, 24, 71, 1, 130, 20, 125, 26, 35, 1, 272, 1, 37, 63, 120, 22, 137, 1, 87, 30, 127, 1
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OFFSET
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1,4
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COMMENTS
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a(n) = omega(n) = 1 iff n is prime.
Not all positive integers are terms of this sequence as many are not expressible as the sum of products defined by the sequence, for example 2, 3, and 6.
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LINKS
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FORMULA
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MAPLE
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with(numtheory):
a:= n-> add(sigma(d)*nops(factorset(n/d)), d=divisors(n)):
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MATHEMATICA
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Table[DivisorSum[n, DivisorSigma[1, #] PrimeNu[n/#] &], {n, 71}] (* Michael De Vlieger, Jan 27 2019 *)
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PROG
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(PARI) a(n) = sumdiv(n, d, sigma(d)*omega(n/d)); \\ Michel Marcus, Jan 22 2019
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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