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A152769
Numbers n such that pi(n) is nonprime.
0
1, 2, 7, 8, 9, 10, 13, 14, 15, 16, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 37, 38, 39, 40, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 61, 62, 63, 64, 65, 66, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99
OFFSET
1,2
COMMENTS
A000720(n) is nonprime.
Complement of A048989.
MATHEMATICA
Select[Range[100], !PrimeQ[PrimePi[#]]&] (* Harvey P. Dale, May 06 2019 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Omar E. Pol, Dec 18 2008
EXTENSIONS
Edited by N. J. A. Sloane, Dec 19 2008
STATUS
approved