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A193348 Number of odd divisors of tau(n). 2
1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 2, 2, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 2, 2, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

a(n) = A001227(A000005(n)). [Reinhard Zumkeller, Jul 25 2011]

LINKS

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

EXAMPLE

a(36) = 3 because tau(36) = 9 and the 3 odd divisors are {1, 3, 9}.

MATHEMATICA

f[n_] := Block[{d = Divisors[DivisorSigma[0, n]]}, Count[OddQ[d], True]]; Table[f[n], {n, 80}]

PROG

(PARI) a(n)=sumdiv(sigma(n, 0), d, d%2);

(PARI) a(n)=n=numdiv(n); numdiv(n>>valuation(n, 2)) \\ Charles R Greathouse IV, Jul 30 2011

CROSSREFS

Cf. A000005.

Sequence in context: A294932 A327804 A056624 * A263723 A318498 A093997

Adjacent sequences:  A193345 A193346 A193347 * A193349 A193350 A193351

KEYWORD

nonn,easy

AUTHOR

Michel Lagneau, Jul 23 2011

STATUS

approved

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Last modified September 22 15:04 EDT 2021. Contains 347607 sequences. (Running on oeis4.)