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A193453
Number of odd divisors of phi(n).
3
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
1,7
COMMENTS
phi(n) : A000010 is the Euler totient function. This sequence equals A193169 (n) for n < 63.
LINKS
FORMULA
a(n) = A001227(A000010(n)) = A000005(A053575(n)). - Antti Karttunen, Dec 04 2017
EXAMPLE
a(63) = 3 because phi(63) = 36 with 3 odd divisors {1, 3, 9}.
MATHEMATICA
f[n_] := Block[{d = Divisors[EulerPhi[n]]}, Count[OddQ[d], True]]; Table[f[n], {n, 80}]
PROG
(PARI) A193453(n) = sumdiv(eulerphi(n), d, d%2); \\ Antti Karttunen, Dec 04 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Jul 26 2011
EXTENSIONS
More terms from Antti Karttunen, Dec 04 2017
STATUS
approved