A152769 Numbers n such that pi(n) is nonprime.

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

Author

Omar E. Pol, Dec 18 2008

Keywords

• easy
• nonn

Comments

A000720(n) is nonprime.

Complement of A048989.

Links

• Omar E. Pol, Divisors and pi(x)

Crossrefs

Cf. A000720, A048989, A141468.

Programs

Mathematica

Select[Range[100],!PrimeQ[PrimePi[#]]&] (* Harvey P. Dale, May 06 2019 *)

Extensions

Edited by N. J. A. Sloane, Dec 19 2008