a(n) = T(2n,n-1), T given by A027157.

Terms

a(0) =3a(1) =10a(2) =76a(3) =264a(4) =2208a(5) =7744a(6) =67776a(7) =238720a(8) =2144768a(9) =7572480a(10) =69203968a(11) =244715520a(12) =2263351296a(13) =8012201984a(14) =74764042240a(15) =264873738240