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

Terms

a(0) =0a(1) =1a(2) =2a(3) =6a(4) =48a(5) =240a(6) =1440a(7) =15120a(8) =120960a(9) =1088640a(10) =14515200a(11) =159667200a(12) =1916006400a(13) =31135104000a(14) =435891456000