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 A127555 #2 Mar 31 2012 10:22:03
%S A127555 4,1,6,4,3,9,3,9,2,0,3,1,3,5,4,9,0,5,3,4,1,3,2,3,9,8,2,8,7,4,3,1,2,1,
%T A127555 9,7,4,1,3,3,3,3,6,9,1,9,2,6,2,3,0,1,1,8,9,1,9,7,6,3,6,7,6,9,0,2,6,4,
%U A127555 9,3,0,8,8,6,1,7,5,2,8,7,1,9,2,4,2,9,6,3,1,1,3,8,9,4,6,3,6,6,6,3
%N A127555 Decimal expansion of the number 4.164393920313549053413239828743... having continued fraction expansion 4, 6, 12, 18, 30, 42, 60, 72, 102, ... (averages of twin primes A014574).
%t A127555 a = {}; Do[If[PrimeQ[Prime[n] + 2], AppendTo[a, Prime[n] + 1]], {n, 2, 500}]; RealDigits[N[FromContinuedFraction[a], 100]][[1]]
%Y A127555 Cf. A064442, A127549, A127550, A127551, A127552, A127553, A127556, A127557, A127558, A127559.
%K A127555 cons,nonn
%O A127555 1,1
%A A127555 _Artur Jasinski_, Jan 18 2007