a(n) = (3n+3)!/(2n+3)!.A001763a(n) = (3n+3)!/(2n+3)!.Terms a(0) =1a(1) =1a(2) =6a(3) =72a(4) =1320a(5) =32760a(6) =1028160a(7) =39070080a(8) =1744364160a(9) =89513424000External referencesoeis: A001763