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A225680 Denominators of phi(n)/n, as n runs through the squarefree numbers (A005117). 4
1, 2, 3, 5, 3, 7, 5, 11, 13, 7, 15, 17, 19, 7, 11, 23, 13, 29, 15, 31, 33, 17, 35, 37, 19, 13, 41, 7, 43, 23, 47, 51, 53, 11, 19, 29, 59, 61, 31, 65, 33, 67, 69, 35, 71, 73, 37, 77, 13, 79, 41, 83, 85, 43, 87, 89, 91, 31, 47, 95, 97, 101, 51, 103, 35, 53, 107 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

To every fraction taken by the arithmetical function m -> phi(m)/m there is exactly one n such that A225679(n)/A225680(n) is equal to it.

LINKS

Ivan Neretin, Table of n, a(n) for n = 1..10000

FORMULA

a(n)=A005117(n)/gcd(A000010(A005117(n)),A005117(n)).

EXAMPLE

A005117(5)=6, phi(6)/6=2/6=1/3, so a(5)=3.

MATHEMATICA

s = Select[Range[200], SquareFreeQ]; Denominator[EulerPhi[s]/s] (* T. D. Noe, May 13 2013 *)

CROSSREFS

Cf. A225679 (numerators).

Sequence in context: A117366 A073482 A318411 * A107685 A161984 A125677

Adjacent sequences:  A225677 A225678 A225679 * A225681 A225682 A225683

KEYWORD

nonn,easy

AUTHOR

Franz Vrabec, May 12 2013

STATUS

approved

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Last modified June 15 22:19 EDT 2019. Contains 324145 sequences. (Running on oeis4.)