T(2n-1,n-2), T given by A027907.

Terms

a(0) =1a(1) =5a(2) =28a(3) =156a(4) =880a(5) =5005a(6) =28665a(7) =165104a(8) =955434a(9) =5550755a(10) =32355917a(11) =189147400a(12) =1108476720a(13) =6510243495a(14) =38308997100a(15) =225810489168