T(2n+1,n+4), T given by A026769.

Terms

a(0) =1a(1) =9a(2) =56a(3) =301a(4) =1506a(5) =7258a(6) =34322a(7) =161039a(8) =755145a(9) =3556269a(10) =16876326a(11) =80881483a(12) =392014244a(13) =1922785012a(14) =9545380884a(15) =47947476888a(16) =243553779646