T(2n-1,n-2), T given by A026703.

Terms

a(0) =1a(1) =7a(2) =39a(3) =203a(4) =1028a(5) =5138a(6) =25502a(7) =126076a(8) =621808a(9) =3062202a(10) =15065888a(11) =74076476a(12) =364066073a(13) =1788762695a(14) =8786918679a(15) =43157674621a(16) =211950770681