A048989 - OEIS

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A048989

Numbers k such that pi(k) is prime.

3

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

(list; graph; refs; listen; history; text; internal format)

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

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