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A370690
Denominator of sigma(phi(n))/phi(sigma(n)), where sigma is the sum of the divisors function and phi is the Euler totient function.
3
1, 2, 2, 2, 2, 4, 1, 8, 1, 6, 2, 12, 3, 2, 8, 2, 6, 2, 8, 4, 4, 2, 2, 16, 5, 3, 16, 6, 1, 8, 2, 36, 8, 18, 4, 18, 18, 16, 2, 24, 2, 8, 5, 4, 2, 2, 2, 60, 3, 10, 8, 7, 9, 32, 4, 8, 32, 3, 8, 48, 5, 4, 48, 2, 6, 8, 2, 4, 8, 4, 1, 8, 12, 36, 2, 48, 4, 4, 4, 20, 11
OFFSET
1,2
COMMENTS
See A370689 for details.
LINKS
Jean-Marie De Koninck and Florian Luca, On the composition of the Euler function and the sum of divisors function, Colloquium Mathematicum, Vol. 108, No. 1 (2007), pp. 31-51.
MATHEMATICA
Table[DivisorSigma[1, EulerPhi[n]]/EulerPhi[DivisorSigma[1, n]], {n, 1, 100}] // Denominator
PROG
(PARI) a(n) = {my(f = factor(n)); denominator(sigma(eulerphi(f)) / eulerphi(sigma(f))); }
CROSSREFS
Cf. A000010, A000203, A033632, A062401, A062402, A065395, A066930 (positions of 1's), A073858, A289336, A289412, A370689 (numerators).
Sequence in context: A086668 A092904 A231883 * A062816 A306653 A132003
KEYWORD
nonn,easy,frac
AUTHOR
Amiram Eldar, Feb 27 2024
STATUS
approved