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 A109401 #3 Mar 30 2012 18:50:50 %S A109401 0,1,1,2,3,4,4,5,6,7,8,9,9,10,11,11,12,13,14,15,15,16,17,17,18,19,20, %T A109401 21,22,23,23,24,25,25,26,26,27,28,29,30,31,32,32,33,34,34,35,35,36,37, %U A109401 38,39,40,41,42,43,43,44,45,45,46,46,47,47,48,49,50,51 %N A109401 Number of primes in the first n terms of A109400. %C A109401 a(n) = Sum(A010051(A109400(m)): 1<=m<=n). %Y A109401 Cf. A000720. %K A109401 nonn %O A109401 1,4 %A A109401 _Reinhard Zumkeller_, Jun 27 2005