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A372836
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a(n) is the numerator of Sum_{d|n, 1 < d < n} 1/d.
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1
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0, 0, 0, 1, 0, 5, 0, 3, 1, 7, 0, 5, 0, 9, 8, 7, 0, 10, 0, 21, 10, 13, 0, 35, 1, 15, 4, 27, 0, 41, 0, 15, 14, 19, 12, 3, 0, 21, 16, 49, 0, 53, 0, 39, 32, 25, 0, 25, 1, 21, 20, 45, 0, 65, 16, 9, 22, 31, 0, 107, 0, 33, 40, 31, 18, 7, 0, 57, 26, 73, 0, 61, 0, 39, 16, 63, 18, 89, 0, 21
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OFFSET
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1,6
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LINKS
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FORMULA
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Numerators of coefficients in expansion of Sum_{k>=2} x^(2*k) / (k * (1 - x^k)).
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EXAMPLE
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0, 0, 0, 1/2, 0, 5/6, 0, 3/4, 1/3, 7/10, 0, 5/4, 0, 9/14, 8/15, 7/8, 0, 10/9, ...
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MATHEMATICA
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nmax = 80; CoefficientList[Series[Sum[x^(2 k)/(k (1 - x^k)), {k, 2, nmax}], {x, 0, nmax}], x] // Numerator // Rest
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PROG
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(PARI) a(n) = numerator(sumdiv(n, d, if ((d>1) && (d<n), 1/d))); \\ Michel Marcus, May 14 2024
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CROSSREFS
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KEYWORD
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nonn,frac
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AUTHOR
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STATUS
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approved
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