a(n) = (2n-1)*(2n-1)!/n.A052145a(n) = (2n-1)*(2n-1)!/n.Terms a(0) =1a(1) =9a(2) =200a(3) =8820a(4) =653184a(5) =73180800a(6) =11564467200External referencesoeis: A052145