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 A106558 #3 Mar 31 2012 13:22:04 %S A106558 3,8,38,264,2896,37638,639830,12156759,279605448,8108557990, %T A106558 251365297667,9300516013674 %N A106558 a(n)=1+floor(sqrt(Pi/2)*p(n)#). %C A106558 a(n) is an approximation to the number of primes less than p(n+1)# %Y A106558 Cf. A000849. %K A106558 nonn %O A106558 1,1 %A A106558 _Pierre CAMI_, May 09 2005