G.f. A(x) satisfies A(x) = 1 + x*A(x)^4*A(-x)^2.

Terms

a(0) =1a(1) =1a(2) =2a(3) =11a(4) =38a(5) =257a(6) =1040a(7) =7646a(8) =33374a(9) =256718a(10) =1171454a(11) =9270560a(12) =43558064a(13) =351490167a(14) =1686018600a(15) =13799914556a(16) =67223728270a(17) =556203232266