a(n) = (5*n)!/((2*n)!*(2*n)!*n!).A001459a(n) = (5*n)!/((2*n)!*(2*n)!*n!).Terms a(0) =1a(1) =30a(2) =3150a(3) =420420a(4) =62355150a(5) =9816086280External referencesoeis: A001459