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

Terms

a(0) =0a(1) =0a(2) =2a(3) =12a(4) =120a(5) =1200a(6) =14400a(7) =191520a(8) =2862720a(9) =47174400a(10) =852768000a(11) =16765056000a(12) =356377190400