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A362470
Number of divisors d of n such that phi(d) | n.
1
1, 2, 1, 3, 1, 4, 1, 4, 1, 2, 1, 6, 1, 2, 1, 5, 1, 6, 1, 5, 1, 2, 1, 8, 1, 2, 1, 3, 1, 4, 1, 6, 1, 2, 1, 9, 1, 2, 1, 7, 1, 6, 1, 3, 1, 2, 1, 10, 1, 2, 1, 3, 1, 8, 1, 4, 1, 2, 1, 8, 1, 2, 1, 7, 1, 4, 1, 3, 1, 2, 1, 12, 1, 2, 1, 3, 1, 4, 1, 9, 1, 2, 1, 11, 1, 2, 1, 4, 1, 6, 1, 3, 1, 2
OFFSET
1,2
FORMULA
a(n) = Sum_{d|n, phi(d)|n} 1.
MATHEMATICA
a[n_] := DivisorSum[n, 1 &, Divisible[n, EulerPhi[#]] &]; Array[a, 100] (* Amiram Eldar, Apr 22 2023 *)
PROG
(PARI) a(n) = sumdiv(n, d, !(n % eulerphi(d))); \\ Michel Marcus, Apr 22 2023
CROSSREFS
Sequence in context: A094741 A360653 A285577 * A324392 A340273 A029234
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, Apr 21 2023
STATUS
approved