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

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =10a(5) =18a(6) =60a(7) =115a(8) =410a(9) =822a(10) =2996a(11) =6174a(12) =22980a(13) =48324a(14) =182328a(15) =389187a(16) =1484410a(17) =3205710a(18) =12329988a(19) =26876586a(20) =104080812a(21) =228606012a(22) =890262984a(23) =1967830254a(24) =7699472676a(25) =17110322908a(26) =67215426440a(27) =150058534620a(28) =591517612616