G.f. satisfies: A(x) = Product_{n>=1} (1 + x^n)*(1 + x^(2*n)*A(x)^2).

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =11a(5) =29a(6) =75a(7) =203a(8) =557a(9) =1561a(10) =4427a(11) =12706a(12) =36819a(13) =107576a(14) =316579a(15) =937471a(16) =2791487a(17) =8352973a(18) =25104573a(19) =75749240a(20) =229379444a(21) =696851166a(22) =2123304184a(23) =6487295518a(24) =19870096689a(25) =61001089214a(26) =187673207413a(27) =578532522637