80179domain: NAppears in sequencesQuartic product sequence: a(n) = Product_{k=1..floor((n-1)/2)} (1 + m*cos(k*Pi/n)^2 + q*cos(k*Pi/n)^4 ), with m = 2*4, q=2*4^3.at n=9A152094a(n) = n*(16*n^2 - 21*n + 7)/2.at n=22A260260a(n) = 2*Sum_{k odd} k!*Stirling2(n,k)/(k + 1).at n=8A281817