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 A137588 #7 Nov 21 2013 12:49:19
%S A137588 0,1,1,1,1,1,2,2,2,2,2,2,3,3,3,3,3,3,4,4,4,4,5,5,5,5,5,5,6,6,6,6,6,6,
%T A137588 6,6,7,7,7,7,7,7,8,8,8,8,9,9,9,9,9,9,10,10,10,10,10,10,10,10,11,11,11,
%U A137588 11,11,11,11,11,11,11,12,12,13,13,13,13,13,13,14,14,14,14,14,14,14,14
%N A137588 Number of primes not greater than n that are greater than the number of primes not greater than n.
%C A137588 a(n) = #{p prime: A000720(n)<p<=n} = A000720(n)-A132090(n);
%C A137588 a(A007821(n)) = n.
%H A137588 R. Zumkeller, <a href="/A137588/b137588.txt">Table of n, a(n) for n = 1..10000</a>
%e A137588 n=100: A000720(100)=25,
%e A137588 a(100)=#{29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97}=16.
%t A137588 Table[PrimePi[n]-PrimePi[PrimePi[n]],{n,90}] (* _Harvey P. Dale_, Mar 20 2011 *)
%K A137588 nonn
%O A137588 1,7
%A A137588 _Reinhard Zumkeller_, Jan 28 2008