T(2n,n-3), T given by A026747.

Terms

a(0) =1a(1) =12a(2) =95a(3) =629a(4) =3781a(5) =21433a(6) =116928a(7) =621317a(8) =3239925a(9) =16662600a(10) =84804868a(11) =428176176a(12) =2148404051a(13) =10726889402a(14) =53349600116a(15) =264499086453