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A370784
a(n) is the denominator of the sum of the reciprocals of the squarefree divisors of the powerful part of n.
2
1, 1, 1, 2, 1, 1, 1, 2, 3, 1, 1, 2, 1, 1, 1, 2, 1, 3, 1, 2, 1, 1, 1, 2, 5, 1, 3, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 3, 1, 1, 2, 7, 5, 1, 2, 1, 3, 1, 2, 1, 1, 1, 2, 1, 1, 3, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 5, 2, 1, 1, 1, 2, 3, 1, 1, 2, 1, 1, 1
OFFSET
1,4
LINKS
FORMULA
a(n) = A332881(A057521(n)).
a(n) = 1 if n is squarefree (A005117).
MATHEMATICA
a[n_] := Denominator[Times @@ (1 + 1/Select[FactorInteger[n], Last[#] > 1 &][[;; , 1]])]; Array[a, 100]
PROG
(PARI) a(n) = {my(f = factor(n)); denominator(prod(i = 1, #f~, if(f[i, 2] == 1, 1, 1 + 1/f[i, 1]))); }
CROSSREFS
Cf. A005117, A057521, A295295, A332881, A370783 (numerators).
Sequence in context: A228349 A285718 A205792 * A249739 A249740 A071773
KEYWORD
nonn,easy,frac
AUTHOR
Amiram Eldar, Mar 02 2024
STATUS
approved