a(n) = f(n,n-2) where f is given in A034261.

Terms

a(0) =1a(1) =3a(2) =14a(3) =65a(4) =294a(5) =1302a(6) =5676a(7) =24453a(8) =104390a(9) =442442a(10) =1864356a(11) =7818538a(12) =32657884a(13) =135950700a(14) =564306840a(15) =2336457645a(16) =9652643910a(17) =39800950530a(18) =163830074100a(19) =673327275390