G.f. A(x) satisfies: A( x - A(x^4)/x^2 ) = x.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =14a(5) =43a(6) =140a(7) =474a(8) =1650a(9) =5865a(10) =21194a(11) =77623a(12) =287492a(13) =1074915a(14) =4051824a(15) =15381073a(16) =58749102a(17) =225621404a(18) =870686810a(19) =3374625925a(20) =13130575110a(21) =51271434788a(22) =200845390668a(23) =789081913225