a(n) = 412*n^6 - 408*n^5 - 1130*n^4 - 360*n^3 + 2368*n^2 - 912*n + 15*(1 - (-1)^n).

Terms

a(0) =0a(1) =0a(2) =0a(3) =118560a(4) =991680a(5) =4465920a(6) =14587200a(7) =38887200a(8) =89965440a(9) =187368960a(10) =359767680a(11) =647427360a(12) =1104978240a(13) =1804481280a(14) =2838790080a(15) =4325210400a(16) =6409455360a(17) =9269898240a(18) =13122120960a(19) =18223760160a(20) =24879648960a(21) =33447256320a(22) =44342422080a(23) =58045389600a(24) =75107134080a(25) =96155988480a(26) =121904565120