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 A220506 #13 Feb 08 2013 18:13:38
%S A220506 0,0,1,2,3,4,5,6,8,9,10,11,13,15,16,18,20,22,24,25,29,30,32,34,36,39,
%T A220506 42,44,46,48,52,54,58,61,62,66,68,72,75,78,81,85,89,92,96,99,101,105,
%U A220506 109,114,118,122,126,129,133,137,141,146,150,154,158,162,167,172,177,181,187,191,195,200
%N A220506 Number of primes <= n-th quarter-square.
%F A220506 a(n) = A000720(A002620(n)), n >= 1.
%t A220506 Table[PrimePi[n^2/4], {n, 75}] (* _Alonso del Arte_, Feb 05 2013 *)
%Y A220506 Partial sums of A220492. A bisection is A038107, n >= 1.
%Y A220506 Cf. A000040, A000720, A002620, A014085, A111208.
%K A220506 nonn
%O A220506 1,4
%A A220506 _Omar E. Pol_, Feb 05 2013