T(2n+1,n+3), T given by A026780.

Terms

a(0) =1a(1) =8a(2) =47a(3) =248a(4) =1251a(5) =6194a(6) =30496a(7) =150348a(8) =745086a(9) =3719388a(10) =18721063a(11) =95045190a(12) =486669349a(13) =2512426480a(14) =13070589618a(15) =68484870582a(16) =361191120212