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

Terms

a(0) =1a(1) =1a(2) =3a(3) =7a(4) =25a(5) =73a(6) =283a(7) =911a(8) =3697a(9) =12561a(10) =52467a(11) =184471a(12) =785929a(13) =2829401a(14) =12229259a(15) =44795167a(16) =195742177a(17) =726541345a(18) =3202144483a(19) =12010174247a(20) =53300753657a(21) =201608659561a(22) =899838791419