a(n) = 4*3*2*1 - 8*7*6*5 + 12*11*10*9 - 16*15*14*13 + ... - (up to the n-th term).

Terms

a(0) =4a(1) =12a(2) =24a(3) =24a(4) =16a(5) =-32a(6) =-312a(7) =-1656a(8) =-1644a(9) =-1524a(10) =-336a(11) =10224a(12) =10208a(13) =9984a(14) =6864a(15) =-33456a(16) =-33436a(17) =-33076a(18) =-26616a(19) =82824a(20) =82800a(21) =82272a(22) =70680a(23) =-172200a(24) =-172172a(25) =-171444a(26) =-152544a(27) =319200a(28) =319168a(29) =318208