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%I #33 Aug 14 2023 10:28:29
%S 2,1,8,1,6,9,4,9,9,0,6,2,4,9,1,2,3,7,3,5,0,3,8,2,2,3,6,1,9,7,1,3,6,5,
%T 0,9,8,1,0,0,2,5,7,6,4,9,8,3,8,1,3,5,7,1,8,4,4,6,2,0,7,1,8,5,5,8,7,7,
%U 1,7,0,5,2,3,4,9,0,8,5,3,7,4,7,5,6,0,0,6,0,0,3,4,9,1,1,5,9,2,8,1
%N Decimal expansion of the volume of an icosahedron with unit edge length.
%H Ivan Panchenko, <a href="/A102208/b102208.txt">Table of n, a(n) for n = 1..1000</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Icosahedron.html">Icosahedron</a>
%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Icosahedron#Area_and_volume">Icosahedron - Area and volume</a>
%H <a href="/index/Al#algebraic_02">Index entries for algebraic numbers, degree 2</a>
%F Equals 5 * (3 + sqrt(5))/12.
%F Equals 5*phi^2/6, phi being the golden ratio. - _Stanislav Sykora_, Nov 23 2013
%e 2.181694990624912373503822...
%t RealDigits[N[5/12*(3+Sqrt[5]),200]][[1]] (* _Vladimir Joseph Stephan Orlovsky_, Feb 21 2011 *)
%o (PARI) 5*(3 + sqrt(5))/12 \\ _G. C. Greubel_, Jul 06 2017
%Y Cf. A001622 (phi), A020829 (regular tetrahedron volume), A131594 (regular octahedron volume), A102769 (regular dodecahedron volume).
%Y Cf. A071402.
%K cons,nonn
%O 1,1
%A Bryan Jacobs (bryanjj(AT)gmail.com), Feb 17 2005
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