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A211780
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a(n) = Sum_{d_<n | n} (d_<n) * tau(n / d_<n), where d_<n = divisors of n that are less than n, tau(x) = A000005(x).
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3
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0, 2, 2, 7, 2, 14, 2, 18, 9, 18, 2, 43, 2, 22, 20, 41, 2, 54, 2, 57, 24, 30, 2, 106, 13, 34, 31, 71, 2, 110, 2, 88, 32, 42, 28, 162, 2, 46, 36, 142, 2, 138, 2, 99, 81, 54, 2, 237, 17, 102, 44, 113, 2, 178, 36, 178, 48, 66, 2, 325, 2, 70, 99, 183, 40, 194, 2
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OFFSET
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1,2
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COMMENTS
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Numbers n such that n divides a(n) are given in A068978.
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LINKS
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FORMULA
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EXAMPLE
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For n = 12: Sum_{d_<n | n} (d_<n) * tau(n / d_<n), = 1*6 + 2*4 + 3*3 + 4*2 + 6*2 = 43.
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MATHEMATICA
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Table[Sum[d*DivisorSigma[0, n/d], {d, Most[Divisors[n]]}], {n, 100}] (* T. D. Noe, Apr 27 2012 *)
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PROG
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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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