From solution to a difference equation.

Terms

a(0) =1a(1) =3a(2) =10a(3) =48a(4) =312a(5) =2520a(6) =24480a(7) =277200a(8) =3588480a(9) =52254720a(10) =845510400a(11) =15048633600a(12) =292190976000