T(2n,n+4), T given by A026747.

Terms

a(0) =1a(1) =11a(2) =79a(3) =472a(4) =2554a(5) =13024a(6) =63958a(7) =306382a(8) =1443463a(9) =6725059a(10) =31101315a(11) =143160979a(12) =657181579a(13) =3012930550a(14) =13810302898a(15) =63339713546a(16) =290848317898