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A069288 Number of odd divisors of n <= sqrt(n). 3
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,9

COMMENTS

a(n) = #{d : d = A182469(n,k), d <= A000196(n), k=1..A001227(n)}. - Reinhard Zumkeller, Apr 05 2015

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

FORMULA

G.f.: sum(n>=1, 1/(1-q^(2*n-1)) * q^((2*n-1)^2) ) [Joerg Arndt, Mar 04 2010]

MATHEMATICA

odn[n_]:=Count[Divisors[n], _?(OddQ[#]&&#<=Sqrt[n ]&)]; Array[odn, 100] (* Harvey P. Dale, Nov 04 2017 *)

PROG

(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

CROSSREFS

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

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Mar 14 2002

STATUS

approved

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Last modified November 22 06:11 EST 2017. Contains 295076 sequences.