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A354870
Number of nonprime squarefree divisors of n.
3
1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 2, 1, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 2, 1, 5, 1, 1, 2, 2, 2, 2, 1, 2, 2, 2, 1, 5, 1, 2, 2, 2, 1, 2, 1, 2, 2, 2, 1, 2, 2, 2, 2, 2, 1, 5, 1, 2, 2, 1, 2, 5, 1, 2, 2, 5, 1, 2, 1, 2, 2, 2, 2, 5, 1, 2, 1, 2, 1, 5, 2, 2, 2, 2, 1, 5, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 1, 5, 1, 2, 5
OFFSET
1,6
COMMENTS
Number of terms of A000469 that divide n.
FORMULA
a(n) = Sum_{d|n} A354819(d).
For all n >= 1, a(n) = a(A046523(n)).
a(n) = A034444(n) - A001221(n). - Ridouane Oudra, Dec 07 2023
MAPLE
with(numtheory): seq(2^nops(factorset(n)) - nops(factorset(n)), n=1..80); # Ridouane Oudra, Dec 07 2023
MATHEMATICA
a[n_] := DivisorSum[n, 1 &, ! PrimeQ[#] && SquareFreeQ[#] &]; Array[a, 100] (* Amiram Eldar, Jun 11 2022 *)
PROG
(PARI)
A354819(n) = ((1!=bigomega(n))&&issquarefree(n));
A354870(n) = sumdiv(n, d, A354819(d));
CROSSREFS
Inverse Möbius transform of A354819.
Differs from A259936 for the first time at n=210, where a(210) = 12, while A259936(210) = 15.
Sequence in context: A323437 A339887 A259936 * A050320 A333175 A294893
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jun 11 2022
STATUS
approved