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%I #28 Oct 18 2019 15:20:42
%S 1,3,10,20,30,40,60,80,120,160,240,320,480,640,960,1280,1920,2560,
%T 3840,5120,7680,10240,15360,20480,30720,40960,61440,81920,122880,
%U 163840,245760,327680,491520,655360,983040
%N Numbers n such that phi(n) = 2^bigomega(n).
%H Harvey P. Dale, <a href="/A089693/b089693.txt">Table of n, a(n) for n = 1..1000</a>
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0,2)
%F a(n) = 2*a(n-2) for n>5. [_Harvey P. Dale_, Mar 01 2012]
%F For n > 2, A001222(a(n)) = 1 + floor(n/2). - _Enrique Pérez Herrero_, Mar 28 2012
%F For n > 1, a(2n) = 5*2^n and a(2n+1) = 15*2^(n-1). - _Enrique Pérez Herrero_, Mar 28 2012
%t Select[Range[100000],EulerPhi[#]==2^PrimeOmega[#]&] (* or *) Join[{1,3,10},LinearRecurrence[{0,2},{20,30},20]] (* _Harvey P. Dale_, Mar 01 2012 *)
%Y Cf. A000010, A061142, A001222, A070004.
%K nonn,easy
%O 1,2
%A _Benoit Cloitre_, Jan 06 2004
%E More terms from _Harvey P. Dale_, Mar 01 2012
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