a(n) = Sum_{k=0..floor(n/3)} (k+1) * 2^k * 3^(n-3*k) * binomial(k,4*(n-3*k)).

Terms

a(0) =1a(1) =0a(2) =0a(3) =4a(4) =0a(5) =0a(6) =12a(7) =0a(8) =0a(9) =32a(10) =0a(11) =0a(12) =80a(13) =240a(14) =0a(15) =192a(16) =2880a(17) =0a(18) =448a(19) =20160a(20) =0a(21) =1024a(22) =107520a(23) =0a(24) =2304a(25) =483840a(26) =20736a(27) =5120a(28) =1935360a(29) =414720