a(n) = (Lucas(6*n) - 2)/16.

Terms

a(0) =0a(1) =1a(2) =20a(3) =361a(4) =6480a(5) =116281a(6) =2086580a(7) =37442161a(8) =671872320a(9) =12056259601a(10) =216340800500