This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A168389 a(n) = PrimePi(A147819(n)). 2
 1, 2, 3, 4, 4, 5, 6, 6, 7, 8, 8, 9, 9, 10, 11, 11, 12, 12, 13, 14, 14, 15, 15, 16, 16, 17, 18, 18, 19, 19, 20, 21, 21, 22, 22, 23, 23, 24, 24, 25, 25, 26, 27, 27, 28, 29, 29, 30, 30, 31, 31, 32, 32, 33, 34, 34, 35, 36, 36, 37, 37, 38, 38, 39, 39, 40, 40, 41, 42, 42, 43, 44, 44, 45 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS MAPLE A147819 := proc(n) if n = 1 then 2; else for a from procname(n-1)+1 do if isprime(a-1) or isprime(a+1) then if a <> 3 then return a; end if; end if; end do ; end if; end proc: A168389 := proc(n) numtheory[pi](A147819(n)) ; end proc: seq(A168389(n), n=1..100) ; # R. J. Mathar, Dec 03 2009 CROSSREFS Cf. A000720, A147819. Sequence in context: A099802 A196266 A112232 * A039708 A189730 A249569 Adjacent sequences:  A168386 A168387 A168388 * A168390 A168391 A168392 KEYWORD nonn AUTHOR Giovanni Teofilatto, Nov 24 2009 EXTENSIONS Extended beyond a(26) by R. J. Mathar, Dec 03 2009 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 15 17:43 EDT 2019. Contains 324142 sequences. (Running on oeis4.)