Numerator of (2*(n+1)!/(n+2)).

Terms

a(0) =1a(1) =4a(2) =3a(3) =48a(4) =40a(5) =1440a(6) =1260a(7) =8960a(8) =72576a(9) =7257600a(10) =6652800a(11) =958003200a(12) =889574400a(13) =11623772160a(14) =163459296000