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A305321
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Expansion of Product_{k>=1} (1 + x^sigma(k)).
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3
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1, 1, 0, 1, 2, 1, 1, 3, 3, 2, 3, 4, 5, 6, 6, 8, 9, 8, 12, 15, 14, 17, 21, 20, 24, 31, 30, 34, 42, 41, 46, 59, 63, 67, 76, 83, 94, 104, 112, 131, 144, 144, 170, 198, 201, 226, 261, 268, 291, 337, 361, 392, 437, 465, 511, 567, 607, 673, 736, 775, 861, 946, 1000
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OFFSET
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0,5
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LINKS
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MAPLE
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with(numtheory):
seq(coeff(series(mul(1+x^sigma(k), k=1..n), x, 80), x, n), n=0..70); # Muniru A Asiru, May 31 2018
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MATHEMATICA
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nmax = 100; CoefficientList[Series[Product[1 + x^DivisorSigma[1, k], {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Jun 03 2018 *)
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PROG
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(PARI) N=99; x='x+O('x^N); Vec(prod(k=1, N, 1+x^sigma(k)))
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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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