T(2n+4,n), array T as in A055216.

Terms

a(0) =1a(1) =6a(2) =28a(3) =113a(4) =423a(5) =1507a(6) =5193a(7) =17469a(8) =57720a(9) =188098a(10) =606336a(11) =1937490a(12) =6146895a(13) =19386189a(14) =60836271a(15) =190104957a(16) =591899346a(17) =1837128933a(18) =5686494333a(19) =17559366768a(20) =54107166250a(21) =166412478896a(22) =510963917688