a(n) = n*A004141(n).

Terms

a(0) =1a(1) =4a(2) =24a(3) =192a(4) =1280a(5) =7680a(6) =48384a(7) =315392a(8) =1916928a(9) =11182080a(10) =72089600a(11) =441188352a(12) =2589982720a(13) =15863644160a(14) =97493975040a(15) =578813952000