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

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =4a(5) =9a(6) =22a(7) =57a(8) =150a(9) =401a(10) =1086a(11) =2972a(12) =8211a(13) =22882a(14) =64250a(15) =181608a(16) =516347a(17) =1475714a(18) =4237134a(19) =12216498a(20) =35355041a(21) =102668187a(22) =299068056a(23) =873654587a(24) =2558849874a(25) =7512707796a(26) =22106301618a(27) =65182852893a(28) =192568585013a(29) =569922496063