a(n) = 2^n*(4^n-3^(n+1)+3*2^n-1)/6.

Terms

a(0) =0a(1) =0a(2) =0a(3) =8a(4) =160a(5) =2080a(6) =22400a(7) =217728a(8) =1989120a(9) =17461760a(10) =149248000a(11) =1252354048a(12) =10373242880a(13) =85129175040a(14) =693959884800