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

Terms

a(0) =1a(1) =0a(2) =1a(3) =2a(4) =4a(5) =11a(6) =33a(7) =99a(8) =310a(9) =1016a(10) =3413a(11) =11682a(12) =40751a(13) =144476a(14) =519013a(15) =1886311a(16) =6928012a(17) =25684055a(18) =96020957a(19) =361742039a(20) =1372442092a(21) =5241062187a(22) =20136335035a(23) =77806111700a(24) =302259125863