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A224834
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a(n) = Sum {d|n, d <= n^(1/2)} tau(d)^2.
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2
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1, 1, 1, 5, 1, 5, 1, 5, 5, 5, 1, 9, 1, 5, 5, 14, 1, 9, 1, 14, 5, 5, 1, 18, 5, 5, 5, 14, 1, 13, 1, 14, 5, 5, 5, 34, 1, 5, 5, 18, 1, 25, 1, 14, 9, 5, 1, 34, 5, 9, 5, 14, 1, 25, 5, 18, 5, 5, 1, 38, 1, 5, 9, 30, 5, 25, 1, 14, 5, 13, 1, 50, 1, 5, 9
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OFFSET
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1,4
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LINKS
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FORMULA
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MAPLE
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f:= proc(n) add(numtheory:-tau(d)^2, d = select(t -> (t^2<=n), numtheory:-divisors(n))) end proc:
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MATHEMATICA
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a[n_] := DivisorSum[n, DivisorSigma[0, #]^2 &, #^2 <= n &]; Array[a, 100] (* Amiram Eldar, Aug 29 2023 *)
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PROG
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(PARI) a(n) = sumdiv(n, d, (d<=sqrtn(n, 2))*numdiv(d)^2) \\ Michel Marcus, Jul 21 2013
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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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