G.f. A(x) satisfies A(x) = 1 + x*(1+x^3)^2*A(x)^2.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =16a(5) =50a(6) =162a(7) =542a(8) =1862a(9) =6521a(10) =23194a(11) =83564a(12) =304340a(13) =1118643a(14) =4144374a(15) =15460134a(16) =58021446a(17) =218918296a(18) =829928124a(19) =3159728783a(20) =12076125224a(21) =46314516352a(22) =178189745050a(23) =687552897730