G.f. satisfies: A(x) = 1 + x*A(x)^3*A(-x)*A(I*x)*A(-I*x).

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =14a(5) =77a(6) =272a(7) =954a(8) =3390a(9) =20942a(10) =81886a(11) =313216a(12) =1200192a(13) =7744531a(14) =31604104a(15) =125795060a(16) =500225166a(17) =3302458490a(18) =13797942732a(19) =56190743623a(20) =228422293810