A362470 Number of divisors d of n such that phi(d) | n.

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

Links

Table of n, a(n) for n=1..94.

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

Cf. A000010, A069932.

Sequence in context: A094741 A360653 A285577 * A324392 A340273 A029234

Adjacent sequences: A362467 A362468 A362469 * A362471 A362472 A362473

Keyword

nonn,easy

Author

Wesley Ivan Hurt, Apr 21 2023

Status

approved