%I
%S 1,2,9,9,0,3,8,1,0,5,6,7,6,6,5,7,9,7,0,1,4,5,5,8,4,7,5,6,1,2,9,4,0,4,
%T 2,7,5,2,0,7,1,0,3,9,4,0,3,5,7,7,8,5,4,7,1,0,4,1,8,5,5,2,3,4,5,8,8,9,
%U 4,9,7,6,2,6,8,1,6,0,0,0,2,7,8,1,0,8,5,9,6,4,0,0,6,7,9,3,6,4,3,1,7,5,6,7,1
%N Decimal expansion of the area of the regular 3gon (triangle) of circumradius = 1. Note this is (1/2)*A104956.
%C Equivalently, the area in the complex plane of the smallest convex set containing all order3 roots of unity.
%H Eric Weisstein et al., <a href="http://mathworld.wolfram.com/RootofUnity.html">"Root of Unity."</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/deMoivreNumber.html">"de Moivre Number."</a>
%F 3*Sqrt[3]/4
%e 1.2990381056766579701455847561294042752071039403577854710418552345889497626816000278108596400679364317567196060615550272724774588...
%t Floor[n/2]*Sin[(2*Pi)/n]  Sin[(4*Pi*Floor[n/2])/n]/2 /. n > 3
%Y Cf. A104955, A104956, A104957.
%K nonn,cons
%O 1,2
%A Joseph Biberstine (jrbibers(AT)indiana.edu), Mar 30 2005
