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A069288
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Number of odd divisors of n <= sqrt(n).
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9
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1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 1, 1, 3, 1, 1, 2, 1, 2, 2, 1, 1, 2, 2, 1, 2, 1, 1, 3, 1, 1, 2, 2, 2, 2, 1, 1, 2, 2, 2, 2, 1, 1, 3, 1, 1, 3, 1, 2, 2, 1, 1, 2, 3, 1, 2, 1, 1, 3, 1, 2, 2, 1, 2, 3, 1, 1, 3, 2, 1, 2, 1, 1, 4
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OFFSET
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1,9
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COMMENTS
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a(n) = #{d : d = A182469(n,k), d <= A000196(n), k=1..A001227(n)}. - Reinhard Zumkeller, Apr 05 2015
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LINKS
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Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
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FORMULA
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G.f.: sum(n>=1, 1/(1-q^(2*n-1)) * q^((2*n-1)^2) ) [Joerg Arndt, Mar 04 2010]
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MATHEMATICA
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odn[n_]:=Count[Divisors[n], _?(OddQ[#]&&#<=Sqrt[n ]&)]; Array[odn, 100] (* Harvey P. Dale, Nov 04 2017 *)
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PROG
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(PARI) a(n) = my(ir = sqrtint(n)); sumdiv(n, d, (d % 2) * (d <= ir)); \\ Michel Marcus, Jan 14 2014
(Haskell)
a069288 n = length $ takeWhile (<= a000196 n) $ a182469_row n
-- Reinhard Zumkeller, Apr 05 2015
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CROSSREFS
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Cf. A001227, A000005, A069289.
Cf. A000196, A182469, A001227.
Sequence in context: A115574 A115577 A115570 * A152831 A097795 A161076
Adjacent sequences: A069285 A069286 A069287 * A069289 A069290 A069291
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KEYWORD
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nonn
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AUTHOR
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Reinhard Zumkeller, Mar 14 2002
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STATUS
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approved
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