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

Terms

a(0) =1a(1) =1a(2) =3a(3) =7a(4) =20a(5) =56a(6) =166a(7) =498a(8) =1530a(9) =4762a(10) =15022a(11) =47862a(12) =153859a(13) =498239a(14) =1623779a(15) =5321059a(16) =17520994a(17) =57937106a(18) =192304222a(19) =640446358a(20) =2139414409a(21) =7166431909a(22) =24065926653a(23) =81003492725a(24) =273229977460a(25) =923438683996