a(n)=(3*n+1)!/(n!*3^n).A079929a(n)=(3*n+1)!/(n!*3^n).Terms a(0) =1a(1) =8a(2) =280a(3) =22400a(4) =3203200a(5) =717516800a(6) =231757926400External referencesoeis: A079929