T(2n,n+4), T given by A026758.

Terms

a(0) =1a(1) =10a(2) =67a(3) =379a(4) =1959a(5) =9597a(6) =45448a(7) =210514a(8) =960942a(9) =4344683a(10) =19525389a(11) =87444051a(12) =390992168a(13) =1747941216a(14) =7821157977a(15) =35055231757a(16) =157484297780a(17) =709447933434