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

Terms

a(0) =1a(1) =2a(2) =0a(3) =0a(4) =0a(5) =-8a(6) =0a(7) =0a(8) =0a(9) =88a(10) =0a(11) =0a(12) =0a(13) =-1248a(14) =0a(15) =0a(16) =0a(17) =20056a(18) =0a(19) =0a(20) =0a(21) =-347360a(22) =0a(23) =0a(24) =0a(25) =6323744a(26) =0a(27) =0a(28) =0a(29) =-119299200