A069288 - OEIS

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A069288

Number of odd divisors of n <= sqrt(n).

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^(2n-1)) q^((2*n-1)^2) ) [Joerg Arndt, Mar 04 2010]`
	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 August 19 23:35 EDT 2017. Contains 290821 sequences.