G.f. A(x) satisfies A(x) = 1/( 1 - x * (1 + 4*x)^(1/2) * A(x) ).

Terms

a(0) =1a(1) =1a(2) =4a(3) =11a(4) =48a(5) =174a(6) =784a(7) =3219a(8) =14816a(9) =65082a(10) =304656a(11) =1393854a(12) =6617184a(13) =31086556a(14) =149336672a(15) =714494467a(16) =3466785216a(17) =16808037474a(18) =82244904016a(19) =402770823114