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%I #23 Jan 07 2019 12:18:37
%S 4,8,9,16,36,72,108,144,216,900,1800,2700,3600,44100,88200
%N Powerful numbers n such that n/phi(n) >= e^gamma*log log n.
%C The sequence is complete.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/TotientFunction.html">Totient Function</a>
%H <a href="/index/Pow#powerful">Index entries for sequences related to powerful numbers</a>
%F A001694 INTERSECT A100966.
%t 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 *)
%o (PARI) a=exp(Euler); for(n=4, 88200, if(ispowerful(n)&&n/eulerphi(n)>=a*log(log(n)), print1(n, ", ")));
%Y Cf. A001694, A100966.
%K nonn,easy,fini,full
%O 1,1
%A _Arkadiusz Wesolowski_, Oct 20 2013
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