G.f. satisfies: A(x) = 1 + x*AGM(A(x)^4, A(-x)^4).

Terms

a(0) =1a(1) =1a(2) =0a(3) =2a(4) =0a(5) =5a(6) =0a(7) =12a(8) =0a(9) =20a(10) =0a(11) =-30a(12) =0a(13) =-546a(14) =0a(15) =-3672a(16) =0a(17) =-18796a(18) =0a(19) =-79640a(20) =0a(21) =-270955a(22) =0a(23) =-584340a(24) =0a(25) =903396a(26) =0a(27) =20471948a(28) =0a(29) =155046180