login
A160709
Centuries containing a prime number of primes.
1
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
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
Sequence in context: A175485 A174657 A231665 * A067113 A101774 A222560
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