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

Terms

a(0) =1a(1) =0a(2) =1a(3) =1a(4) =5a(5) =10a(6) =38a(7) =101a(8) =353a(9) =1070a(10) =3659a(11) =11843a(12) =40505a(13) =135873a(14) =468104a(15) =1604375a(16) =5576315a(17) =19386656a(18) =67950717a(19) =238676813a(20) =842797959a(21) =2983745508a(22) =10603445402a(23) =37777263153a(24) =134985354179a(25) =483438728094