a(n) = [x^n] Product_{k=1..n} 1/(x^(2*k)*(1-x^k)).

Terms

a(0) =1a(1) =1a(2) =5a(3) =27a(4) =169a(5) =1115a(6) =7760a(7) =55748a(8) =411498a(9) =3101490a(10) =23785645a(11) =185064559a(12) =1457664666a(13) =11602828475a(14) =93205739436a(15) =754751603157