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A293713 Numbers n such that phi(psi(n))/n < phi(psi(m))/m for all m < n, where phi is Euler's totient function (A000010) and psi is the Dedekind psi function (A001615). 0
1, 3, 4, 5, 11, 17, 23, 25, 29, 59, 89, 149, 179, 239, 269, 359, 377, 389, 419, 839, 1049, 1259, 1889, 2099, 2309, 9239, 11549, 13859, 20789, 23099, 25409, 30029, 90089, 180179, 210209, 270269, 300299, 330329, 390389, 420419, 540539, 570569, 1017917, 1018013 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Sândor proved that lim inf phi(psi(n))/n = 0, hence this sequence is infinite.

REFERENCES

Jôzsef Sândor, On Dedekind’s arithmetical function, Seminarul de Teoria Structurilor, Univ. Timisoara, No. 51, 1988, pp. 1-15.

LINKS

Table of n, a(n) for n=1..44.

Jôzsef Sândor, On the composition of some arithmetic functions, II, Journal of Inequalities in Pure and Applied Mathematics, Vol. 6, Issue 3, Article 73 (2005).

MATHEMATICA

psi[n_] := If[n < 1, 0, n*Sum[MoebiusMu[d]^2/d, {d, Divisors@n}]]; a={}; rm=2; Do[r=EulerPhi[psi[n]]/n; If[r<rm, rm=r; AppendTo[a, n]], {n, 1, 10^5}]; a

CROSSREFS

Cf. A000010, A001615.

Sequence in context: A276470 A152911 A317768 * A280255 A276542 A318077

Adjacent sequences:  A293710 A293711 A293712 * A293714 A293715 A293716

KEYWORD

nonn

AUTHOR

Amiram Eldar, Oct 15 2017

STATUS

approved

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Last modified October 16 20:09 EDT 2021. Contains 348044 sequences. (Running on oeis4.)