E.g.f. (1-2x)/(1-2x-x^2+x^3).

Terms

a(0) =1a(1) =0a(2) =2a(3) =6a(4) =72a(5) =720a(6) =10080a(7) =156240a(8) =2822400a(9) =56972160a(10) =1280966400a(11) =31654022400a(12) =853580851200