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

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =6a(5) =13a(6) =32a(7) =84a(8) =230a(9) =646a(10) =1846a(11) =5344a(12) =15632a(13) =46128a(14) =137148a(15) =410469a(16) =1235670a(17) =3739182a(18) =11367528a(19) =34703126a(20) =106343338a(21) =326994496a(22) =1008620692a(23) =3120022642a(24) =9676739056a(25) =30085166398a(26) =93745106004a(27) =292716273248a(28) =915764667556