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

Terms

a(0) =1a(1) =1a(2) =0a(3) =1a(4) =1a(5) =4a(6) =0a(7) =5a(8) =2a(9) =13a(10) =6a(11) =40a(12) =24a(13) =150a(14) =100a(15) =583a(16) =315a(17) =1928a(18) =899a(19) =5781a(20) =2594a(21) =16966a(22) =7857a(23) =51206a(24) =25509a(25) =163112a(26) =86794a(27) =545710a(28) =305266a(29) =1896760