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%I #2 Mar 30 2012 17:37:48
%S 2,3,19,37,719,1511,5443,69709,386093,1907819,10777931,17819101,
%T 18653749,56125547,60163267,98911811,272887613,567611663,989060309,
%U 2444540149
%N Numbers n such that n=prime(phi(sigma(pi(n)))).
%C It is obvious that all terms are primes. There is no further term up to 5*10^9.
%t Do[If[n=Prime[m];m==EulerPhi[DivisorSigma[1,PrimePi[n]]],Print[n]],{m,235000000}]
%Y Cf. A000010, A000040, A000720, A000203, A163666.
%K more,nonn
%O 1,1
%A _Farideh Firoozbakht_, Aug 04 2009