a(n) = (n+1)!^2/2^n.A184358a(n) = (n+1)!^2/2^n.Terms a(0) =1a(1) =2a(2) =9a(3) =72a(4) =900a(5) =16200a(6) =396900a(7) =12700800a(8) =514382400a(9) =25719120000External referencesoeis: A184358