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%I #7 Apr 10 2018 21:47:57
%S 2,3,5,7,11,17,19,23,31,41,53,59,67,83,97,103,109,127,131,157,179,191,
%T 211,227,241,277,283,311,331,353,367,401,419,431,461,509,547,563,587,
%U 599,617,661,691,709,719,739,773,797,859,877,919,967,991,1009,1031
%N Prime numbers of prime-power index.
%C A prime index of n is a number m such that prime(m) divides n.
%F a(n) = A000040(A000961(n)).
%t Prime/@Select[Range[100],Or[#===1,PrimePowerQ[#]]&]
%o (PARI) forprime(p=1, 500, if(p==2 || isprimepower(primepi(p)), print1(p, ", "))) \\ _Felix Fröhlich_, Apr 10 2018
%Y Cf. A000040, A000961, A001222, A005117, A007097, A056239, A063834, A275024, A281113, A302242, A302491, A302492.
%K nonn
%O 1,1
%A _Gus Wiseman_, Apr 08 2018