a(n) = A027082(n, 2n-6).

Terms

a(0) =1a(1) =1a(2) =5a(3) =17a(4) =57a(5) =190a(6) =623a(7) =2010a(8) =6395a(9) =20103a(10) =62561a(11) =193062a(12) =591637a(13) =1802551a(14) =5465275a(15) =16503365a(16) =49665179a(17) =149033583a(18) =446131159a(19) =1332749213a(20) =3974445543a(21) =11834777320a(22) =35196098205a(23) =104558824915a(24) =310332568225a(25) =920350334943