Sequence defined by a(2*n) = 2*(n^2 + 2*n) and a(2*n-1) = (2*n)!/n!.

Terms

a(0) =0a(1) =2a(2) =6a(3) =12a(4) =16a(5) =120a(6) =30a(7) =1680a(8) =48a(9) =30240a(10) =70a(11) =665280a(12) =96a(13) =17297280a(14) =126a(15) =518918400a(16) =160a(17) =17643225600a(18) =198a(19) =670442572800a(20) =240a(22) =286a(24) =336a(26) =390a(28) =448