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 A188719 #7 Mar 31 2012 10:27:23
%S A188719 2,7,25,115,670,4324,30657,229568,1775675,14156112,115500275,960392564
%N A188719 Number of safe primes < 10^n.
%C A188719 Number of safe primes with at most n digits; or a(10^n).
%H A188719 Wikipedia, <a href="http://en.wikipedia.org/wiki/Safe_prime">Safe prime</a>
%e A188719 a(10^2) = a(100) = #{5, 7, 11, 23, 47, 59, 83} = 7
%Y A188719 A156875, A006880, A005385
%K A188719 nonn
%O A188719 1,1
%A A188719 _Krzysztof Ostrowski_, Apr 09 2011