

A074920


Integers k such that phi(k) = 6k/Pi^2 rounded to nearest integer.


2



1, 2, 3, 4, 33, 39, 99, 3237, 9711, 2069301, 6207903, 45502509, 24091595067
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OFFSET

1,2


COMMENTS

The average value of phi(n) can be approximated for large n by 6n/Pi^2 (Tattersall, p. 162).


REFERENCES

James J. Tattersall, "Elementary Number Theory in Nine Chapters", Cambridge University Press, 2001.


LINKS

Table of n, a(n) for n=1..13.


EXAMPLE

phi(99) = 60 and 6*99/Pi^2 = 60.1848...., which rounds off to 60. Hence 99 is a term of the sequence.


MATHEMATICA

s = Pi^2; l = {}; Do[ If[Abs[EulerPhi[n]  6 n/ s] <= 0.5, l = Append[l, n]], {n, 1, 10^5}]; l


CROSSREFS

Cf. A000010, A072355.
Cf. A059956 (6/Pi^2).
Sequence in context: A067242 A028354 A028355 * A180631 A102842 A299169
Adjacent sequences: A074917 A074918 A074919 * A074921 A074922 A074923


KEYWORD

nonn,more


AUTHOR

Joseph L. Pe, Oct 01 2002


EXTENSIONS

a(10)a(13) from Amiram Eldar, May 10 2019
Name edited by Michel Marcus, May 10 2019


STATUS

approved



