Expansion of x*(1-3*x)*(1-x)/(1-7*x+14*x^2-7*x^3).

Terms

a(0) =1a(1) =3a(2) =10a(3) =35a(4) =126a(5) =462a(6) =1715a(7) =6419a(8) =24157a(9) =91238a(10) =345401a(11) =1309574a(12) =4970070a(13) =18874261a(14) =71705865a(15) =272491891a(16) =1035680954a(17) =3936821259a(18) =14965658694a(19) =56893879910a(20) =216295686467a(21) =822315097387