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%I #15 Jul 08 2023 04:01:52
%S 2,1,8,6,2,7,6,0,3,5,4,6,5,2,8,3,9,6,0,2,9,8,7,8,6,2,8,0,7,6,3,7,4,5,
%T 1,2,9,9,5,3,7,5,4,7,0,4,3,6,5,1,0,0,3,3,0,0,1,5,2,4,6,4,6,2,9,8,5,9,
%U 0,4,3,6,0,3,8,2,2,3,2,5,4,3,2,4,0,6,4,3,2,2,2,7,5,6,4,8,8,9,9,4
%N Decimal expansion of arccos(-sqrt(1/3)).
%C Dihedral angle between mixed type faces of the truncated octahedron. - _R. J. Mathar_, Mar 24 2012
%H G. C. Greubel, <a href="/A195698/b195698.txt">Table of n, a(n) for n = 1..5000</a>
%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Truncated_octahedron">Truncated Octahedron</a>.
%F Equals Pi - arcsin(sqrt(2/3)) = Pi - arctan(sqrt(2)). - _Amiram Eldar_, Jul 08 2023
%e arccos(-1/sqrt(3)) = 2.1862760354...
%t (See A195695.)
%t RealDigits[ArcCos[-1/Sqrt[3]], 10, 50][[1]] (* _G. C. Greubel_, Nov 18 2017 *)
%o (PARI) acos(-1/sqrt(3)) \\ _G. C. Greubel_, Nov 18 2017
%o (Magma) [Arccos(-1/Sqrt(3))]; // _G. C. Greubel_, Nov 18 2017
%Y Cf. A195695.
%K nonn,cons
%O 1,1
%A _Clark Kimberling_, Sep 23 2011
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