Expansion of e.g.f. 1/(1-x^2-3*x^3).

Terms

a(0) =1a(1) =0a(2) =2a(3) =18a(4) =24a(5) =720a(6) =7200a(7) =45360a(8) =1128960a(9) =14152320a(10) =199584000a(11) =4909766400a(12) =82388275200