a(n) = (4*n+6)(!^4)/6(!^4).A051618a(n) = (4*n+6)(!^4)/6(!^4).Terms a(0) =1a(1) =10a(2) =140a(3) =2520a(4) =55440a(5) =1441440a(6) =43243200a(7) =1470268800a(8) =55870214400External referencesoeis: A051618