A160709 Centuries containing a prime number of primes.

5, 14, 15, 20, 26, 30, 33, 35, 37, 39, 40, 45, 52, 55, 56, 60, 62, 63, 66, 70, 73, 75, 81, 87, 88, 89, 91, 93, 94, 96, 97, 98, 101, 108, 112, 115, 120, 122, 125, 131, 135, 140, 143, 155, 157, 166, 167, 168, 171, 175, 182, 183, 184, 185, 188, 189, 191, 192, 193, 196

Offset

1,1

Links

H. v. Eitzen, Table of n, a(n) for n = 1..10000

Formula

{n: A038822(n) is in A000040}.

Example

a(1) = 5 because 5 is the first Century to have a prime number (17) of primes.

Maple

A038822 := proc(n) numtheory[pi](n*100)-numtheory[pi]((n-1)*100) ; end: A160709 := proc(n) option remember ; local a; if n = 1 then 5 ; else for a from procname(n-1)+1 do if isprime( A038822(a) ) then RETURN(a) ; fi; od: fi; end: seq(A160709(n), n=1...90) ; # R. J. Mathar, May 27 2009

Mathematica

Select[Range[200], PrimeQ[PrimePi[100#]-PrimePi[100(#-1)]]&] (* Harvey P. Dale, Oct 03 2011 *)

Crossrefs

Cf. A000040, A038822.

Sequence in context: A175485 A174657 A231665 * A067113 A101774 A222560

Adjacent sequences: A160706 A160707 A160708 * A160710 A160711 A160712

Keyword

easy,nonn

Author

Jonathan Vos Post, May 25 2009

Extensions

Extended by Ray Chandler, May 25 2009

More terms from R. J. Mathar, May 27 2009

Status

approved