%I #8 Sep 15 2016 23:40:55
%S 2,6,5,5,5,8,6,5,7,8,7,1,1,1,5,0,7,7,5,7,3,7,1,3,0,2,5,1,2,7,4,6,9,4,
%T 3,0,3,8,2,6,2,0,6,3,0,2,5,6,4,7,3,0,4,9,0,8,1,0,1,1,9,3,1,3,8,3,9,3,
%U 8,6,4,5,0,3,1,9,7,1,0,2,2,9,8,8,7,8,1,9,6,7,4,2,6,0,1,1,3,7,9,8,2,5,1,8,5
%N Decimal expansion of the solid angle (in steradians) subtended by a cone having the 'magic' angle A195696 as its polar angle.
%C An example of such a cone is the one circumscribed to a cube from one of its vertices. When expressed as a fraction of the full solid angle, this constant leads to A156309.
%H Stanislav Sykora, <a href="/A273621/b273621.txt">Table of n, a(n) for n = 1..2000</a>
%F Equals 2*Pi*(1-sqrt(1/3)) = 4*Pi*A156309 = 2*Pi*(1-cos(A210974)).
%e 2.65558657871115077573713025127469430382620630256473049081011931...
%t First@RealDigits@N[2*Pi*(1 - Sqrt[1/3]), 25] (* _G. C. Greubel_, Aug 15 2016 *)
%o (PARI) 2*Pi*(1-sqrt(1/3))
%Y Cf. A000796, A156309, A195696, A210974.
%K nonn,cons
%O 1,1
%A _Stanislav Sykora_, Aug 15 2016
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