a(n) = 3*(4*n+2)!/(3*n+3)!.A370057a(n) = 3*(4*n+2)!/(3*n+3)!.Terms a(0) =1a(1) =3a(2) =30a(3) =546a(4) =14688a(5) =526680a(6) =23680800a(7) =1282554000a(8) =81339793920External referencesoeis: A370057