A227243 Powerful numbers n such that n/phi(n) >= e^gamma*log log n.

4, 8, 9, 16, 36, 72, 108, 144, 216, 900, 1800, 2700, 3600, 44100, 88200

Offset

1,1

Comments

The sequence is complete.

Links

Table of n, a(n) for n=1..15.

Eric Weisstein's World of Mathematics, Totient Function

Index entries for sequences related to powerful numbers

Formula

A001694 INTERSECT A100966.

Mathematica

PowerfulQ[1] := True; PowerfulQ[n_Integer?Positive] := Min[Last /@ FactorInteger[n]] > 1; Select[Range[100], PowerfulQ[#] && #/EulerPhi[#] >= E^EulerGamma*Log[Log[#]] &] (* G. C. Greubel, Oct 02 2017 *)

Prog

(PARI) a=exp(Euler); for(n=4, 88200, if(ispowerful(n)&&n/eulerphi(n)>=a*log(log(n)), print1(n, ", ")));

Crossrefs

Cf. A001694, A100966.

Sequence in context: A285438 A089042 A340093 * A272575 A020145 A202271

Adjacent sequences: A227240 A227241 A227242 * A227244 A227245 A227246

Keyword

nonn,easy,fini,full

Author

Arkadiusz Wesolowski, Oct 20 2013

Status

approved