a(n) = Product_{k=0..n} C(n+k+2, n+2).A120248a(n) = Product_{k=0..n} C(n+k+2, n+2).Terms a(0) =1a(1) =4a(2) =75a(3) =7056a(4) =3457440a(5) =9032601600External referencesoeis: A120248