G.f. C(x) satisfies: C(C(x)) + S(S(x)) = x where S(C(x)) = 2*x*C(x).

Terms

a(0) =1a(1) =0a(2) =0a(3) =-4a(4) =0a(5) =0a(6) =-64a(7) =0a(8) =0a(9) =-2432a(10) =0a(11) =0a(12) =-125952a(13) =0a(14) =0a(15) =-8086016a(16) =0a(17) =0a(18) =-598302720a(19) =0a(20) =0a(21) =-49260396544a(22) =0a(23) =0a(25) =0a(26) =0a(28) =0a(29) =0a(31) =0a(32) =0