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%I #5 Mar 30 2012 17:37:48
%S 2,5,47,107,1613,5653,21557,230047,821603,8145173,47073007,68939141,
%T 76040521,196388147,240595631,433046543,1085166671,2269551127,
%U 4670405591,9784786813,104484802043,420065905307,474962067289,2616252796471,5804170333301
%N Numbers n such that n=prime(sigma(phi(pi(n)))).
%C It is obvious that all terms are primes.
%F a(n) = A000040(A018784(n))
%t Do[If[n=Prime[m];m==DivisorSigma[1,EulerPhi[PrimePi[n]]],Print[n]],{m,235000000}]
%Y Cf. A000010, A000040, A000720, A000203, A163665.
%K nonn
%O 1,1
%A _Farideh Firoozbakht_, Aug 04 2009
%E Formula and six more terms from _Max Alekseyev_, Jun 25 2011
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