G.f. satisfies A(x) = (1 - 9*x*A(x))^(1/3).

Terms

a(0) =1a(1) =-3a(2) =0a(3) =9a(4) =27a(5) =0a(6) =-324a(7) =-1215a(8) =0a(9) =18711a(10) =75816a(11) =0a(12) =-1301265a(13) =-5484996a(14) =0a(15) =100048689a(16) =431943435a(17) =0a(18) =-8192222064a(19) =-35942240565a(20) =0a(21) =700434986472a(23) =0a(26) =0a(29) =0