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A369257
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a(n) = number of odd divisors of n that have an even number of prime factors with multiplicity.
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4
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1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 2, 1, 1, 2, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 1, 3, 1, 1, 1, 2, 2, 2, 1, 1, 2, 2, 1, 2, 1, 1, 2, 1, 1, 3, 1, 2, 2, 1, 1, 2, 2, 1, 2, 1, 1, 3, 1, 2, 2, 1, 1, 3, 1, 1, 2, 2, 1, 2, 1, 1, 3, 2, 1, 2, 1, 2, 1, 1, 2, 3, 2, 1, 2, 1, 1, 4
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OFFSET
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1,9
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LINKS
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FORMULA
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From _Antti Karttunen_, Jan 27 2024: (Start)
Dirichlet g.f.: (zeta(s)^2*(1-2^-s) + zeta(2s)*(1+2^-s)) / 2.
(End)
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EXAMPLE
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Of the eight odd divisors of 105, the four divisors 1, 15, 21, 35 all have an even number of prime factors (A001222(d) is even), therefore a(105) = 4.
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PROG
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(PARI)
A353557(n) = ((n%2)&&(!(bigomega(n)%2)));
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CROSSREFS
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Inverse Möbius transform of A353557.
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KEYWORD
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nonn
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AUTHOR
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_Antti Karttunen_, Jan 24 2024
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STATUS
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approved
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