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A069289
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Sum of odd divisors of n <= sqrt(n).
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11
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1, 1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 4, 1, 1, 4, 1, 1, 4, 1, 1, 4, 1, 1, 4, 6, 1, 4, 1, 1, 9, 1, 1, 4, 1, 6, 4, 1, 1, 4, 6, 1, 4, 1, 1, 9, 1, 1, 4, 8, 6, 4, 1, 1, 4, 6, 8, 4, 1, 1, 9, 1, 1, 11, 1, 6, 4, 1, 1, 4, 13, 1, 4, 1, 1, 9, 1, 8, 4, 1, 6, 13, 1, 1, 11, 6, 1, 4, 1
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OFFSET
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1,9
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COMMENTS
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LINKS
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FORMULA
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G.f.: Sum_{k>=1} (2*k - 1) * x^((2*k - 1)^2) / (1 - x^(2*k - 1)). - Ilya Gutkovskiy, Apr 04 2020
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MATHEMATICA
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Table[Total[Select[Divisors[n], OddQ[#]&&#<=Sqrt[n]&]], {n, 120}] (* Harvey P. Dale, Jul 16 2017 *)
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PROG
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(PARI) a(n) = my(ir = sqrtint(n)); sumdiv(n, d, (d % 2) * (d <= ir) * d); \\ Michel Marcus, Jan 14 2014
(Haskell)
a069289 n = sum $ takeWhile (<= a000196 n) $ a182469_row n
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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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