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

Terms

a(0) =1a(1) =2a(2) =10a(3) =72a(4) =696a(5) =8400a(6) =121680a(7) =2056320a(8) =39715200a(9) =862928640a(10) =20832940800a(11) =553246848000