a(n) = (2*n+1)*(n-1)!.

Terms

a(0) =3a(1) =5a(2) =14a(3) =54a(4) =264a(5) =1560a(6) =10800a(7) =85680a(8) =766080a(9) =7620480a(10) =83462400a(11) =997920000a(12) =12933043200a(13) =180583603200