A Somos-4 variant.

Terms

a(0) =1a(1) =2a(2) =8a(3) =24a(4) =112a(5) =736a(6) =3776a(7) =40192a(8) =391424a(9) =4203008a(10) =85312512a(11) =1270368256a(12) =32235102208