A063865(4n-3).

Terms

a(0) =2a(1) =8a(2) =70a(3) =722a(4) =8220a(5) =99820a(6) =1265204a(7) =16547220a(8) =221653776a(9) =3025553180a(10) =41931984034a(11) =588491482334