A193453 Number of odd divisors of phi(n).

1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 2, 2, 1, 1, 1, 2, 3, 1, 2, 2, 2, 1, 2, 2, 3, 2, 2, 1, 4, 1, 2, 1, 2, 2, 3, 3, 2, 1, 2, 2, 4, 2, 2, 2, 2, 1, 4, 2, 1, 2, 2, 3, 2, 2, 3, 2, 2, 1, 4, 4, 3, 1, 2, 2, 4, 1, 2, 2, 4, 2, 3, 3, 2, 3, 4, 2, 4, 1, 4, 2, 2, 2, 1, 4, 2, 2, 2, 2, 3, 2, 4, 2, 3, 1, 2, 4, 4, 2, 3, 1, 4, 2, 2

Offset: 1

Author

Michel Lagneau, Jul 26 2011

Keywords

• nonn

Comments

phi(n) : A000010 is the Euler totient function. This sequence equals A193169 (n) for n < 63.

Examples

			a(63) = 3 because phi(63) = 36 with 3 odd divisors {1, 3, 9}.
		

Links

• Antti Karttunen, Table of n, a(n) for n = 1..16384

Crossrefs

Cf. A000010, A001227, A053575.

Programs

Mathematica

f[n_] := Block[{d = Divisors[EulerPhi[n]]}, Count[OddQ[d], True]]; Table[f[n], {n, 80}]

PARI

A193453(n) = sumdiv(eulerphi(n), d, d%2); \\ Antti Karttunen, Dec 04 2017

Formula

a(n) = A001227(A000010(n)) = A000005(A053575(n)). - Antti Karttunen, Dec 04 2017

Extensions

More terms from Antti Karttunen, Dec 04 2017