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A225679 Numerators of phi(n)/n, as n runs through the squarefree numbers (A005117). 4
1, 1, 2, 4, 1, 6, 2, 10, 12, 3, 8, 16, 18, 4, 5, 22, 6, 28, 4, 30, 20, 8, 24, 36, 9, 8, 40, 2, 42, 11, 46, 32, 52, 8, 12, 14, 58, 60, 15, 48, 10, 66, 44, 12, 70, 72, 18, 60, 4, 78, 20, 82, 64, 21, 56, 88, 72, 20, 23, 72, 96, 100, 16, 102, 16, 26, 106, 108, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

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

Table of n, a(n) for n=1..69.

FORMULA

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

EXAMPLE

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

MATHEMATICA

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

CROSSREFS

Cf. A225680 (denominators).

Sequence in context: A171233 A096907 A249146 * A081879 A066248 A065164

Adjacent sequences:  A225676 A225677 A225678 * A225680 A225681 A225682

KEYWORD

nonn,easy

AUTHOR

Franz Vrabec, May 12 2013

STATUS

approved

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Last modified May 23 20:23 EDT 2019. Contains 323528 sequences. (Running on oeis4.)