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) ; [From R. J. Mathar, Jan 30 2010]