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A293714 Numbers n such that phi(phi(n))/n < phi(phi(m))/m for all m < n, where phi is Euler's totient function (A000010). 0
1, 2, 3, 4, 6, 14, 18, 42, 90, 186, 198, 210, 450, 462, 930, 990, 1050, 2310, 7350, 14910, 16170, 66990, 169050, 177870, 371910, 1540770, 2312310, 4626930, 4834830, 19711230, 20030010, 30060030, 60150090, 62852790 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..34.

MATHEMATICA

f[n_] := EulerPhi[EulerPhi[n]]/n; a={}; fm=10^10; Do[f1=f[k]; If[f1<fm , fm=f1; AppendTo[a, k]], {k, 1, 10^6}]; a

PROG

(PARI) lista(nn) = {my(rmin = 2); for (n=1, nn, if ((r=eulerphi(eulerphi(n))/n) < rmin, rmin = r; print1(n, ", ")); ); }

CROSSREFS

Cf. A000010, A010554.

Sequence in context: A188715 A174046 A095991 * A049911 A056712 A204540

Adjacent sequences:  A293711 A293712 A293713 * A293715 A293716 A293717

KEYWORD

nonn,more

AUTHOR

Amiram Eldar, Oct 15 2017

EXTENSIONS

a(26)-a(34) from Michel Marcus, Oct 18 2017

STATUS

approved

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Last modified September 26 20:34 EDT 2021. Contains 347672 sequences. (Running on oeis4.)