A121647 Sequence gives values of sigma(n)^2 divided by UnitarySigma(n)*UnitaryPhi(n) associated with n in A121556.

1, 3, 2, 6, 4, 3, 9, 2, 8, 6, 7, 4, 5, 12, 7, 3, 4, 10, 9, 7, 2, 5, 8, 6, 5, 14, 4, 10, 7, 5, 7, 5, 12, 10, 4, 3, 9, 14, 3, 10, 8, 10, 11, 15, 4, 9, 4, 2, 9, 3, 5, 6, 4, 7, 2, 8, 5, 15, 4, 11, 4, 5, 10, 16, 7, 10, 6, 13, 9, 2, 6, 7, 5, 4, 4, 6, 2, 8, 2, 15, 5, 8, 4, 11, 10, 12, 8

Offset: 1

Author

Yasutoshi Kohmoto Sep 12 2006

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000203, A034448, A047994, A121556.

Programs

Mathematica

f[p_, e_] := (p^(e+1)-1)^2/(p-1)^2/(p^(2*e)-1); ratio[1] = 1; ratio[n_] := Times @@ (f @@@ FactorInteger[n]); Select[ratio /@ Range[10^5], IntegerQ] (* Amiram Eldar, Dec 11 2019 *)

Formula

a(n) = f(A121556(n)), where f(m) = A000203(m)^2/(A034448(m)*A047994(m)). - Amiram Eldar, Dec 11 2019

Extensions

Extended with the aid of b121556.txt. - R. J. Mathar, Sep 04 2018