G.f. satisfies: A(x - x^3) = x^3 - x^9.

Terms

a(0) =1a(1) =0a(2) =3a(3) =0a(4) =12a(5) =0a(6) =54a(7) =0a(8) =264a(9) =0a(10) =1365a(11) =0a(12) =7344a(13) =0a(14) =40698a(15) =0a(16) =230736a(17) =0a(18) =1332045a(19) =0a(20) =7803900a(21) =0a(22) =46280520a(23) =0a(24) =277294752a(25) =0a(26) =1676056044a(27) =0a(28) =10207492512a(29) =0