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%I #14 Feb 24 2013 15:31:23
%S 0,0,0,0,7,24,63,110,242,360,650,812,1425,1680,2737,2718,4788,5200,
%T 7812,8272,12075,11328,17875,18486,25542,26264,35438
%N Number of intersections of diagonals in the exterior of a regular n-gon.
%H Bjorn Poonen; Michael Rubinstein, <a href="http://math.mit.edu/~poonen/papers/ngon.pdf">The Number of Intersection Points Made by the Diagonals of a Regular Polygon</a>, SIAM J. Discrete Mathematics 11 (1998), nr. 1, pp. 135-156; doi: <a href="http://dx.doi.org/10.1137/S0895480195281246">10.1137/S0895480195281246</a>; arXiv: <a href="http://arXiv.org/abs/math.MG/9508209">math.MG/9508209</a>.
%H Eric Weisstein, <a href="http://mathworld.wolfram.com/RegularPolygonDivisionbyDiagonals.html">Regular Polygon Division by Diagonals</a> (MathWorld).
%F a(n) = 1/24*n*(n-3)*(n-5)*(2*n-11) for n odd
%Y Cf. A006561.
%K nonn,more
%O 3,5
%A _Martin Renner_, Feb 07 2013
%E a(17)-a(29) from _Martin Renner_, Feb 24 2013
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