a(n) = n!*(n+3)! / 3!.A010792a(n) = n!*(n+3)! / 3!.Terms a(0) =1a(1) =4a(2) =40a(3) =720a(4) =20160a(5) =806400a(6) =43545600a(7) =3048192000a(8) =268240896000External referencesoeis: A010792