%I #8 Apr 06 2018 17:40:10
%S 6,12,18,24,42,60
%N Numbers n such that to phi(n) = pi(n)-1.
%e 9 primes below 24 = {2,3,5,7,11,13,17,19,23}; RRS[24]={1,5,7,11,13,17,19,23}, so 24 is here.
%t Do[s=EulerPhi[n]-PrimePi[n]; If[Equal[s, -1], Print[n]], {n, 1, 10000}]
%Y Cf. A037228, A037171, A000010, A000720.
%K fini,full,nonn
%O 1,1
%A _Labos Elemer_, Aug 02 2002