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

Terms

a(0) =0a(1) =1a(2) =4a(3) =21a(4) =124a(5) =782a(6) =5144a(7) =34845a(8) =241196a(9) =1697498a(10) =12104872a(11) =87246770a(12) =634425752a(13) =4647805372a(14) =34267130928a(15) =254035385949