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 A200113 #21 Oct 30 2018 10:31:02
%S A200113 4,1,9,5,2,9,9,2,3,6,1,3,8,0,8,9,2,4,2,5,2,7,8,6,7,3,1,3,4,4,1,3,4,9,
%T A200113 6,9,9,5,5,6,6,2,8,1,4,2,3,8,7,4,0,0,7,5,0,7,4,1,1,5,0,0,5,6,4,7,5,0,
%U A200113 2,4,3,0,7,4,1,5,4,5,1,8,7,5,7,3,8,3
%N A200113 Decimal expansion of the area K of cyclic pentagon with sides 2, 3, 5, 7, and 11.
%C A200113 s = {2,3,5,7,11}; R = circumradius (A200257).
%C A200113 K = sum((s(n)/4)(4*R^2-s(n)^2)^(1/2), n=1..5) = 41.9529923613808924252...
%C A200113 This is maximal area of pentagon with sides 2, 3, 5, 7, 11.
%t A200113 digits = 86; r = x /. FindRoot[ Sum[ ArcSin[ Prime[n]/2/x], {n, 5}] == Pi, {x, 5}, WorkingPrecision -> digits+10] // Re; Sum[p/4*(4*r^2 - p^2)^(1/2), {p, Prime /@ Range[5]}] // RealDigits[#, 10, digits]& // First (* _Jean-François Alcover_, Feb 15 2013, after _Zak Seidov_ *)
%Y A200113 Cf. A200257.
%K A200113 nonn,cons
%O A200113 2,1
%A A200113 _Zak Seidov_, Nov 18 2011