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

Author

Arkadiusz Wesolowski, Oct 20 2013

Keywords

• nonn
• easy
• fini
• full

Comments

The sequence is complete.

Links

• Eric Weisstein's World of Mathematics, Totient Function
• Index entries for sequences related to powerful numbers

Crossrefs

Cf. A001694, A100966.

Programs

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 *)

PARI

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

Formula

A001694 INTERSECT A100966.