a(n) = a(n-1)!/a(n-2)!; a(0) = 1, a(1) = 3.A019437a(n) = a(n-1)!/a(n-2)!; a(0) = 1, a(1) = 3.Terms a(0) =1a(1) =3a(2) =6a(3) =120External referencesoeis: A019437