a(n) = Sum_{k=0..floor(n/3)} 2^k * 3^(n-3*k) * binomial(k+6,6) * binomial(k,2*(n-3*k)).

Terms

a(0) =1a(1) =0a(2) =0a(3) =14a(4) =0a(5) =0a(6) =112a(7) =336a(8) =0a(9) =672a(10) =6048a(11) =0a(12) =3360a(13) =60480a(14) =30240a(15) =14784a(16) =443520a(17) =665280a(18) =59136a(19) =2661120a(20) =7983360a(21) =1816320a(22) =13837824a(23) =69189120a(24) =42282240a(25) =64576512a(26) =484323840a(27) =583751168a(28) =339026688a(29) =2905943040