A289412 a(n) = denominator of (sigma(n) / phi(n)).

1, 1, 1, 2, 2, 1, 3, 4, 6, 2, 5, 1, 6, 1, 1, 8, 8, 2, 9, 4, 3, 5, 11, 2, 20, 2, 9, 3, 14, 1, 15, 16, 5, 8, 1, 12, 18, 3, 3, 8, 20, 1, 21, 5, 4, 11, 23, 4, 14, 20, 4, 12, 26, 3, 5, 1, 9, 14, 29, 2, 30, 5, 9, 32, 4, 5, 33, 16, 11, 1, 35, 8, 36, 6, 10, 9, 5, 1

Offset: 1

Author

Jaroslav Krizek, Aug 19 2017

Keywords

• nonn
• frac

Comments

a(n) = 1 for numbers in A020492 (balanced numbers).

Examples

			For n = 7, sigma(7) / phi(7) = 8/6 = 4/3, a(n) = 3.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A289336 (numerators).

Cf. A000010, A000203, A018894, A020492, A023897, A055234, A070032, A070033.

Programs

Magma

[Denominator(SumOfDivisors(n) / EulerPhi(n)): n in[1..1000]]

Mathematica

Array[Denominator[DivisorSigma[1, #]/EulerPhi[#]] &, 78] (* Michael De Vlieger, Aug 19 2017 *)

PARI

a(n) = denominator(sigma(n)/eulerphi(n)); \\ Michel Marcus, Aug 21 2017

Formula

a(n) = denominator of (A000203(n) / A000010(n)).