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A000720(a(n)) is prime. [From Omar E. Pol, Dec 19 2008]
T. D. Noe, Table of n, a(n) for n=1..10000
Select[Range, PrimeQ[PrimePi[#]]&] (* Harvey P. Dale, Mar 23 2011 *)
Sequence in context: A215249 A089912 A047425 * A299299 A103402 A154664
Adjacent sequences: A048986 A048987 A048988 * A048990 A048991 A048992
G. L. Honaker, Jr.