(A047926(n)-A091588(n))/2.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =2a(5) =5a(6) =15a(7) =43a(8) =127a(9) =383a(10) =1143a(11) =3423a(12) =10264a(13) =30785