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%I #27 May 14 2020 17:21:21
%S 1,3,47,88,200,547,12182,15335,39104,58122,73282,150740,480886
%N n is such that pi(n*prime(n))/n is an integer.
%C a(9) > 30000. - _Michel Marcus_, Sep 02 2019
%C a(13) > 200000. - _Giovanni Resta_, Sep 02 2019
%t Do[s=PrimePi[n*Prime[n]]/n; If[IntegerQ[s], Print[n]], {n, 1, 100000}]
%t Select[Range[16000],IntegerQ[PrimePi[#*Prime[#]]/#]&] (* _Harvey P. Dale_, Jul 23 2015 *)
%o (PARI) isok(n) = denominator(primepi(n*prime(n))/n) == 1; \\ _Michel Marcus_, Sep 02 2019
%Y Cf. A000040, A000720, A033286, A057855, A084297, A084298.
%K nonn,hard,more
%O 1,2
%A _Labos Elemer_, May 27 2003
%E Corrected by _Harvey P. Dale_, Jul 23 2015
%E a(9)-a(12) from _Giovanni Resta_, Sep 02 2019
%E a(13) from _Chai Wah Wu_, May 14 2020
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