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

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =15a(5) =45a(6) =142a(7) =464a(8) =1556a(9) =5327a(10) =18532a(11) =65326a(12) =232826a(13) =837589a(14) =3037472a(15) =11092143a(16) =40753626a(17) =150541422a(18) =558762382a(19) =2082871613a(20) =7794301294a(21) =29269317708a(22) =110263451242a(23) =416595676681