This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A166724 #5 Jan 19 2019 20:25:44 %S A166724 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, %T A166724 12,12,13,14,14,14,14,15,15,15,15,15,16,16,16,16,17,17,18,18,18,18,19, %U A166724 19,19,20,20,21,21,21,21,21,22,22,22,23,23,23,23,23,24,24,24,24,24,24,24 %N A166724 a(n) = PrimePi(A166546(n)). %p A166724 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 %Y A166724 Cf. A166546. %K A166724 easy,nonn %O A166724 1,3 %A A166724 _Giovanni Teofilatto_, Oct 20 2009 %E A166724 Corrected (one 14 inserted) by _R. J. Mathar_, Jan 30 2010