a(n) = 2*(n!)^2.A048617a(n) = 2*(n!)^2.Terms a(0) =2a(1) =2a(2) =8a(3) =72a(4) =1152a(5) =28800a(6) =1036800a(7) =50803200a(8) =3251404800a(9) =263363788800External referencesoeis: A048617