A048989 Numbers k such that pi(k) is prime.

3, 4, 5, 6, 11, 12, 17, 18, 31, 32, 33, 34, 35, 36, 41, 42, 59, 60, 67, 68, 69, 70, 83, 84, 85, 86, 87, 88, 109, 110, 111, 112, 127, 128, 129, 130, 157, 158, 159, 160, 161, 162, 179, 180, 191, 192, 211, 212, 213, 214, 215, 216, 217, 218, 219

Offset

1,1

Comments

A000720(a(n)) is prime. - Omar E. Pol, Dec 19 2008

Links

T. D. Noe, Table of n, a(n) for n = 1..10000

Mathematica

Select[Range[250], PrimeQ[PrimePi[#]]&]  (* Harvey P. Dale, Mar 23 2011 *)

Prog

(PARI) isok(k) = isprime(primepi(k)); \\ Michel Marcus, Jan 15 2023

Crossrefs

Cf. A000720.

Sequence in context: A215249 A089912 A047425 * A356050 A299299 A103402

Adjacent sequences: A048986 A048987 A048988 * A048990 A048991 A048992

Keyword

nonn,easy,nice

Author

G. L. Honaker, Jr.

Status

approved