a(n) = (3*n + 1)!/(n!)^3.A331322a(n) = (3*n + 1)!/(n!)^3.Terms a(0) =1a(1) =24a(2) =630a(3) =16800a(4) =450450a(5) =12108096a(6) =325909584a(7) =8779605120a(8) =236637794250External referencesoeis: A331322