1198287271domain: NAppears in sequencesa(n) = 2^n*Product_{k=1..floor((n-1)/2)} (1 + 2*cos(k*Pi/n)^2 + 4*cos(k*Pi/n)^4).at n=26A152090a(n) = Product_{k=1..floor((n-1)/2)} (1 + 4*sin(k*Pi/n)^2 + 16*sin(k*Pi/n)^4).at n=26A152142