Expansion of o.g.f. 2*(1+x)^2/(1-2*x+sqrt(1-8*x)).

Terms

a(0) =1a(1) =5a(2) =20a(3) =96a(4) =528a(5) =3136a(6) =19584a(7) =126720a(8) =841984a(9) =5710848a(10) =39376896a(11) =275185664a(12) =1944821760a(13) =13875707904a(14) =99807723520a(15) =722997411840