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).

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

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: A369849 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