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%I #14 Jan 19 2026 15:38:33
%S 3,4,10,20,44,60,583,677,947,1182,12048,16018,74316
%N Numbers k such that 3^k + phi(k) is prime.
%C All terms correspond to certified primes (Primo 2.2.0 beta). No more terms through 10000.
%C a(14) > 10^5. - _Donovan Johnson_, Feb 06 2010
%t Do[If[PrimeQ[3^n + EulerPhi[n]], Print[n]], {n, 1, 10000}]
%Y Cf. A000010 (phi), A109889.
%K nonn,hard,more
%O 1,1
%A _Ryan Propper_, Aug 31 2005
%E a(11)-a(13) from _Donovan Johnson_, Feb 06 2010