%I #2 Mar 30 2012 17:34:28
%S 1,1,1,12,15,99,120,725,861,5092,5995,35223,41328,242265,283881,
%T 1662716,1947351,11402203,13351528,78166989,91523685,535804116,
%U 627341331,3672559727,4299936480,25172370289,29472399505,172534703340
%N a(n)=2*Product[(1 + 4*Cos[k*Pi/n]^2)*(1 + 4*Sin[k*Pi/n]^2), {k, 1, Floor[(n - 1)/2]}] - Product[(1 + 4*Sin[k*Pi/n]^2), {k, 1, Floor[(n - 1)/2]}].
%C It appears that Limit[Sqrt[a[n+2]/a[n]],n->Infinity]=1+(Sqrt[5]+1)/2.
%t f[n_] = 2*Product[(1 + 4*Cos[k*Pi/n]^2)*(1 + 4*Sin[k*Pi/n]^2), {k, 1, Floor[(n - 1)/2]}] - Product[(1 + 4*Sin[k*Pi/n]^2), {k, 1, Floor[(n - 1)/2]}]; Table[N[f[n]], {n, 0, 30}]; Floor[%]
%K nonn
%O 0,4
%A _Roger L. Bagula_, Nov 28 2008