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

Terms

a(0) =1a(1) =2a(2) =9a(3) =28a(4) =88a(5) =270a(6) =808a(7) =2386a(8) =6960a(9) =20104a(10) =57607a(11) =163950a(12) =463907a(13) =1306104a(14) =3661248a(15) =10223820a(16) =28452400a(17) =78941412a(18) =218426608a(19) =602886704a(20) =1660329597a(21) =4563175466a(22) =12517834605a(23) =34280427828a(24) =93729509848a(25) =255900484218a(26) =697712467704