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 A272042 #13 Apr 20 2016 05:08:19
%S A272042 4,11,21,31,47,61,69,87,99,113,127,141,161,171,179,209,219,241,259,
%T A272042 275,289,307,315,357,361,377,399,419,433,449,459,491,497,535,549,567,
%U A272042 589,603,627,645,663,685,695,721,729
%N A272042 a(n) = 2*prime(2n) - prime(n).
%F A272042 a(n) = 3n*log n + 3n*log log n - (3-log 2)*n + O(n log log n/log n). - _Charles R Greathouse IV_, Apr 18 2016
%F A272042 a(n) = A072473(n) + A031215(n). - _R. J. Mathar_, Apr 20 2016
%e A272042 For n=1, 2*prime(2*1)-prime(1) = 2*3 - 2 = 4.
%e A272042 For n=10, 2*prime(2*10)-prime(10) = 2*71 - 29 = 113.
%t A272042 Table[2*Prime[2 n] - Prime[n], {n, 1, 45}]
%o A272042 (PARI) a(n) = 2*prime(2*n) - prime(n) \\ _Charles R Greathouse IV_, Apr 18 2016
%K A272042 nonn,easy
%O A272042 1,1
%A A272042 _Andres Cicuttin_, Apr 18 2016