a(n) = 3*(n-2)*(n-3)*(3*n^2-9)*(3*n^2-9*n-5)/2.

Terms

a(0) =0a(1) =0a(2) =819a(3) =14850a(4) =87318a(5) =327060a(6) =947025a(7) =2314494a(8) =5011020a(9) =9902088a(10) =18216495a(11) =31635450a(12) =52391394a(13) =83376540a(14) =128261133a(15) =191621430a(16) =279077400a(17) =397440144a(18) =554869035a(19) =761038578a(20) =1027314990a(21) =1366942500a(22) =1795239369a(23) =2329803630a(24) =2990728548a(25) =3800827800a(26) =4785870375a(27) =5974825194