a(n) = 4^n * [x^n] sqrt(1-x) * Product_{k>=1} (1 + x^k).

Terms

a(0) =1a(1) =2a(2) =6a(3) =84a(4) =198a(5) =1660a(6) =8348a(7) =38632a(8) =172358a(9) =1015020a(10) =4815796a(11) =21693720a(12) =112008732a(13) =512079960a(14) =2529630072a(15) =12483215056a(16) =56441387078a(17) =264961478476