A166724 a(n) = PrimePi(A166546(n)).

0, 1, 2, 3, 3, 4, 4, 4, 5, 5, 6, 6, 6, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 10, 11, 11, 11, 11, 11, 12, 12, 12, 13, 14, 14, 14, 14, 15, 15, 15, 15, 15, 16, 16, 16, 16, 17, 17, 18, 18, 18, 18, 19, 19, 19, 20, 20, 21, 21, 21, 21, 21, 22, 22, 22, 23, 23, 23, 23, 23, 24, 24, 24, 24, 24, 24, 24

Offset: 1

Author

Giovanni Teofilatto, Oct 20 2009

Keywords

• easy
• nonn

Crossrefs

Cf. A166546.

Programs

Maple

A166546 := proc(n) option remember; local a; if n = 1 then 1; else for a from procname(n-1)+1 do if isprime(1+numtheory[tau](a)) then return a; end if; end do ; end if; end proc: A166724 := proc(n) numtheory[pi](A166546(n)) ; end proc: seq(A166724(n),n=1..80) ; # R. J. Mathar, Jan 30 2010

Extensions

Corrected (one 14 inserted) by R. J. Mathar, Jan 30 2010